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	MX-5 Miata Forum > MX-5 Miata Discussion > NC (2006+) > NC Maintenance
Differential Fluid Change @ 10,000 miles?

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NC Maintenance How to keep your NC in top running condition. This section focuses on maintaining and fixing the stock NC - not about modifications.

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21st January 2011, 05:52	#1
Lone Wlf First gear Join Date: Jun 2010 Location: CA Posts: 30	Differential Fluid Change @ 10,000 miles? Just had my new (to me) 2010 6 speed MT in for its first oil change at 5500 miles. The mechanic suggested that at around 10k miles it might be a good idea to change the diff fluid because there could be metal shavings in it since the car's new. I'm not mechanical enough to know whether this is a good idea or a waste of money. What do you guys think, and why? Thanks.
21st January 2011, 08:00	#2
hepcatz Moderator Join Date: May 2008 Location: Fairfax, VA Posts: 3,458	Some do change early and it won't be harmful, however the mazda service schedule lists at 48 months or 60,000 miles. I did mine early at around 12,000 miles as I wanted to upgrade the brand used. I personally won't make/pay for a service visit just to do this however if it is already going to be in then I might have it done. More info from mazda below: https://www.mymazda.com/MusaWeb/sear...2&modelId=1710 __________________ Everything I needed to know about life I learned from watching Bob Ross http://autocrossr.blogspot.com/
21st January 2011, 09:17	#3
mx5mia Sixth Gear Join Date: Mar 2006 Location: S-East, PA. PACE Miata Club Posts: 5,931	I changed the rear diff lube around 10,000 miles in my 06. I wanted to change to synthetic, and this time frame worked out well. I have the T/F limited slip diff. The fluid was really black. "I have heard" some of the blackness came from the ring and pinion gears seating, and some from the clutch packs seating into each other. As black as it was, I am glad I changed it if for only that reason. At 20,000 miles I put the Motorcraft XT-M5-QS in my 6 spd tranny, and thought while it was up on jack stands I might as well drain out the rear diff and refill it with the left over differential lube I had from before. The fluid that came out was only darkened a little. My one uncle used to be in charge of a fleet of vehicles for the state, he always said that "oil and grease is cheaper than parts and labor". I tend to follow that line of thinking too. __________________ 06 Winning Blue GT, aka Mxie; 6mt, Sport Susp Pkg, Prem Pkg 2, X-Pel Clr Bra, Wolo Air Horn, RoadsterSport Q & Mid-Pipe, RX8 Red/Yellow Sways, & Kansai FST Brace. 2006 Winning Blue Registry Link

21st January 2011, 09:43	#4
RubyDoo Supporting Member Join Date: Nov 2009 Location: Driftless Zone Posts: 10,581	If it's a standard diff on that 06 it probably is not critical, because it's not so precise and complicated as a limited slip version. The drain plugs on the diff and tranny have a magnet that will catch and hold filings anyway. Surprised he did not suggest the tranny ... unless he was nervous about it. Changing that fluid would be better. Search here for info on "Motorcraft Full Synthetic" for loads of info about tranny fluid for you. Even if you are not having troubles, it's nice to put some quality stuff in there for the long run. Before you do the next oil change, post back with a price that they ask change the diff and tranny fluids. Folks will let you know if it is reasonable. It's an incredibly easy job to do yourself with a $10 hand pump to put the new fluids in. But it does involve getting the car up in the air, crawling under, etc. Depending where you are in CA, I bet you could find a member nearby to do it with you, and give you a guided tour of the bottom of your car at the same time. Well worth the effort! In fact, consider doing that for your next oil change, and installing a Fumoto valve at the same time. It will help prevent future greasemonkeys from screwing up your oil drain plug. Welcome to miatadom! __________________ When something goes wrong, I'm the first to admit it and the last one to know.  ~Paul Simon
21st January 2011, 10:22	#5
wooo Wheels flew off Join Date: Nov 2006 Location: NS Canada Posts: 24,268	Quote: Originally Posted by Lone Wlf .... I'm not mechanical enough to know whether this is a good idea or a waste of money. What do you guys think, and why? ... I changed mine at about 3k miles and glad I did. The old stuff came out black and sludgy, and there was metal present. Not saying necessarily that this is a problem, but I'm sure the baby appreciated the clean new stuff.  Used one quart (liter?) of Mobil1 synthetic GL5 gear oil. Cost ~$10. Took about 1/2 hour to change. It came in a sorta squeeze bottle with spout, so no funnel or pump was necessary. Changed it again at ~20k miles. Surely overkill, but babies are meant to be babied. And it's sorta satisfying to do these simple jobs yourself.  A much more useful alternative to the F. valve, is a "suck it out the dipstick" device. It's on my short list of must have tools. Right up there with the clamp-on DC meter and the digital vernier calipers.  __________________ 2007 Copper Red NC GT PRHT 6AT; 2011 Ranger XLT AT Supercab 4x4;  2007 Bombardier RXP fluid drive; 2012 Renegade Sport 600 Ace with CVT.

21st January 2011, 10:35	#6
humfrz Wheels flew off Join Date: Oct 2005 Location: Puyallup, Washington Posts: 20,967	Quote: Originally Posted by Lone Wlf ........... What do you guys think, and why? Thanks. If it makes you feel better, I'd suggest you have it done, although I don't think it's necessary. Why? I donno......just to feel better...?? Oh, have some NC Tips.... http://forum.miata.net/vb/attachment...9&d=1290147156 humfrz
21st January 2011, 11:28	#7
Raven18940 Third gear Join Date: Nov 2010 Location: Greater DC Area Posts: 413	I'd make sure you work the clutch packs a little before you dump the fluid if you have a LSD. Want to get all the break in wear over with to old oil so the new oil will stay clean longer. If you have no LSD, dump it when it's convenient.  You'll like the synthetic oil on cold mornings. I know my drivetrain feels like glue first thing in the morning when it's in the 20F's out. Why did Mazda use conventional oil in the gearbox and diff???  __________________ Currently miataless 2011 Mazda 2

23rd January 2011, 10:13	#8
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	Differential oil change on a new rear…..You should change the fluid at around 600 to 1,000 miles. You say why?????? You are breaking in a new gear box the first few hundred miles are going to make the most friction and wear in the shortest period of time than the full life of the rear end.  This is true of the open standard rear or the LSD equipped rear. The LSD rear has a little bit more friction going on than the standard open but both types of 3rd member share all other same components. The NC and NB Miata rear takes just shy of a quart/liter to fill….over filling is bad….Why????? Because the oil can foam from lack of ventilation. Filling the case is easy….fill to the oil starts to come back out the fill hole. Let the oil flow back out on a level surface till it slows to a trickle/drip then replace the fill plug. The rear has a proper level doing it this way and you have no second guessing if it is right.  What should I use for oil????? A good 75/110 or 75/140 standard or synthetic oil as long as it is a GL-5. Stay away from Royal Purple gear lube use wall mart brand before this over priced substandard stuff. But my book says 75/90?????? The 75/90 of old is the new 75/110 the 75/110 has taken the place of the 75/90 in lubricating properties. What brand of oil should I use? Amsoil brand is the best and the best priced for the top of the line lubricants. Mobil 1, Red Line, Valvoline are also very good choices. Change the fluid again in 5000 miles doing this will get the rest of the break in debris out. Refill and change ones a year or 2. The total cost of this doing it your self is about $45 on the high side and $30 on the low side. It’s cheap insurance to assure a proper long lasting gear box.  Be sure to inspect and clean the magnetic drain plug. If you see large metal pieces or heavy metallic in the oil this is cause for inspection under warranty. There is always going to be some metallic on the drain plug and in the old oil this is normal.  Do a little research on all I tell you, you will understand I’m not giving opinion just fact. __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver
23rd January 2011, 17:49	#9
humfrz Wheels flew off Join Date: Oct 2005 Location: Puyallup, Washington Posts: 20,967	^........very good, informative post, S2KPuddyDad ....... humfrz

23rd January 2011, 19:21	#10
RubyDoo Supporting Member Join Date: Nov 2009 Location: Driftless Zone Posts: 10,581	Point of info for new readers on the forum: S2KPuddyDad is a specialist in rear ends, and we're talking about the metal kind in his avatar, not the other kind. So his post here is the authoritative final word. Ignore everything hacks like me said before. __________________ When something goes wrong, I'm the first to admit it and the last one to know.  ~Paul Simon
23rd January 2011, 20:35	#11
Raven18940 Third gear Join Date: Nov 2010 Location: Greater DC Area Posts: 413	I don't understand the logic of using 75W-140 instead of 75W-90. Everyone seems to be moving to lighter oils that reduce drag (5W-20 instead of 5W-30 for example). Why the reversal of the trend? __________________ Currently miataless 2011 Mazda 2

23rd January 2011, 21:40	#12
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	Quote: Originally Posted by Raven18940 I don't understand the logic of using 75W-140 instead of 75W-90. Everyone seems to be moving to lighter oils that reduce drag (5W-20 instead of 5W-30 for example). Why the reversal of the trend? There is nothing trendy about gear box lubricant. The design of the hypoid differential gear box is old school and has not been improved on like the engine and transmissions have been over the years. The Mazda gear box differential calls for a SAE 90W from the factory using a 75/90w may not give adequate protection. Your safe bet is a 75/110 GL-5 hypoid oil.  In 2006 the oil standards changed Please read,  “The need for redefined classifications centered on the wide variation in kinematic viscosity possible for SAE 90 and SAE 140 grade lubricant. In the prior version of SAE J306, these ranges were so broad that lubricant viscosity could vary greatly and still technically be in grade. Two new viscosity grades were introduced to cover the upper end of the specifications, SAE 110 and SAE 190. The more narrowly defined classification provides OEMs with greater flexibility in specifying a viscosity grade to ensure an optimal balance of fuel economy and durability for their equipment. In addition, under the old designations, an axle could be serviced with a lubricant having a viscosity significantly lower or higher than the lubricant with which the axle was validated. To prevent the axle from being filled with a lubricant with too low a viscosity, an OEM was forced to specify a higher viscosity grade than actually desired. For example, under the old classifications, if the optimum 100°C viscosity for an axle was 19.5 cSt, the OEM would normally specify an SAE 90 lubricant. However, the actual viscosity of this lubricant could be as low as 13.5 cSt, which might be too low to provide the required durability. To prevent this problem, the OEM would recommend an SAE 140 grade lubricant, ensuring that viscosity would never fall below 19.5 cSt. Unfortunately, that also means viscosity could be as high as 41.0 cSt, possibly resulting in poor fuel economy or shift problems. Under the new limits, the OEM would recommend SAE 110 grade lubricant, which meets the 19.5 cSt requirements and ensures that the axle is serviced with a lubricant having a viscosity no higher than 31 cSt. A Question of Balance  OEMs are challenged today to meet the often conflicting demands for improved fuel economy coupled with improved axle durability. Government regulations are dictating better fuel economy, while vehicle owners are demanding increased performance. Engine horsepower has increased by 34% over the last decade, but axle gear sizes have remained constant, sump capacities have been reduced, and drain intervals have been extended. These demanding conditions can be met only by axle lubricants that provide enhanced durability protection. Axle efficiency can be improved by using lower viscosity fluids (such as SAE 75W-90), which minimize frictional churning losses. However, light trucks and SUVs are often used in conditions that expose axles to heavy loads or high operating temperatures. These conditions require superior axle protection, often provided by choosing a heavier viscosity fluid (SAE 75W-140, for example). Commercial vehicle applications may have even more stringent durability requirements. However, providing high durability and long vehicle life often reduces fuel efficiency. The new viscosity classifications provide more flexibility for OEMs to select the optimum viscosity grade for an application. For example, the SAE 110 grade should be useful in an SUV or light duty truck where improved fuel economy is important but high torque or durability at high speed operation is essential. This new classification should aid OEMs in specifying a fluid viscosity more tightly to ensure that the lubricant has the intended physical properties for a given application. The SAE 190 grade may allow better efficiency and enable multigrade performance in severe duty applications where high film strengths are needed. These end uses may include applications such as construction equipment operated in extreme temperature environments. The end result is a better match of fluid performance to axle needs. __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver
23rd January 2011, 22:26	#13
Raven18940 Third gear Join Date: Nov 2010 Location: Greater DC Area Posts: 413	Quote: Originally Posted by S2KPuddyDad The Mazda gear box differential calls for a SAE 90W from the factory using a 75/90w may not give adequate protection. I fail to see how a 75W-90 oil doesn't meet the viscosity requirements of a SAE 90 oil. The 90 is the important number in 75W-90, it means it conforms to SAE 90 specs at operating temperature. The 75W only means it's thinner than SAE 90 when cold, like yesterday when it's 18F outside here. That SAE 90 gear oil felt like glue.  Anyway, back on topic. Since it says the manufacturers are specing thicker oils than they need so their diffs always have oil thick enough, it seems reasonable to assume that any SAE 90 should fit the bill. However, the real question here is what is the the viscosity of the OEM oil because then it should be fairly easy to find a multi-grade synthetic to match. __________________ Currently miataless 2011 Mazda 2

23rd January 2011, 22:37	#14
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	Quote: Originally Posted by Raven18940 I fail to see how a 75W-90 oil doesn't meet the viscosity requirements of a SAE 90 oil. The 90 is the important number in 75W-90, it means it conforms to SAE 90 specs at operating temperature. The 75W only means it's thinner than SAE 90 when cold, like yesterday when it's 18F outside here. That SAE 90 gear oil felt like glue.  Anyway, back on topic. Since it says the manufacturers are specing thicker oils than they need so their diffs always have oil thick enough, it seems reasonable to assume that any SAE 90 should fit the bill. However, the real question here is what is the the viscosity of the OEM oil because then it should be fairly easy to find a multi-grade synthetic to match. It is a long read but the answer is there. Some brands of 75/90 will fall below safe standards for our rear requirements. If you wish to use 75/90 go to your brand of choice web site and find out if it meets the standards many do not. Or even more easy…..USE 75/110 it’s a no brainer Just a little FYI to you track junkies use 75/140 or an SAE 190 the stock LSD will perform much better __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver
23rd January 2011, 22:51	#15
Raven18940 Third gear Join Date: Nov 2010 Location: Greater DC Area Posts: 413	Quote: Originally Posted by S2KPuddyDad It is a long read but the answer is there. Some brands of 75/90 will fall below safe standards for our rear requirements. If you wish to use 75/90 go to your brand of choice web site and find out if it meets the standards many do not. My question is what are the "safe" standards? What cSt at 100C?  Will the 15.2 cSt of M1 75W-90 meet the specs or does the oil need to be thicker? EDIT: Basically, I may not know everything about rears, but I know a lot about oil. I'm open to using non-factory spec oil, but not without damn good reason. The gear oil standard change has been in effect as long as the NC has been around, so I don't really buy the "110 is the new 90" argument. __________________ Currently miataless 2011 Mazda 2

23rd January 2011, 23:15	#16
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	Quote: Originally Posted by Raven18940 My question is what are the "safe" standards? What cSt at 100C?  Will the 15.2 cSt of M1 75W-90 meet the specs or does the oil need to be thicker? EDIT: Basically, I may not know everything about rears, but I know a lot about oil. I'm open to using non-factory spec oil, but not without damn good reason. The gear oil standard change has been in effect as long as the NC has been around, so I don't really buy the "110 is the new 90" argument. Since our rear requires a SAE 90W you need a cst of 19.5 This is why the change and why the old 75/90 is the new 75/110 You need to use 75/110 Also note your owners manual states no 75/90 available through Mazda for your differential  SAE 90W or 80/90W as a second 2 main reasons for diff failure is driver error and inadequate lubrication __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver
24th January 2011, 08:22	#17
Raven18940 Third gear Join Date: Nov 2010 Location: Greater DC Area Posts: 413	Quote: Originally Posted by S2KPuddyDad Since our rear requires a SAE 90W you need a cst of 19.5 See, this is the disconnect here. Because if I read the specs right SAE 90 should be a minimum of 13.5, not 19.5. So how do you know they meant 110 when they said 90? Maybe they meant 90? The MX-5 isn't exactly a torque monster. __________________ Currently miataless 2011 Mazda 2

24th January 2011, 09:25	#18
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	Quote: Originally Posted by Raven18940 See, this is the disconnect here. Because if I read the specs right SAE 90 should be a minimum of 13.5, not 19.5. So how do you know they meant 110 when they said 90? Maybe they meant 90? The MX-5 isn't exactly a torque monster. Most 75/ 90w will fall below 13.5 this number is not a safe minimum. Standards are 19.5 for your Miata differential. The Miata diff case only holds about 900ML of fluid not much for a lot of heat and shear going on inside our differential. If you need more reassurance please do more research on your computer or just use what you think is best....Good luck __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver
24th January 2011, 09:31	#19
wooo Wheels flew off Join Date: Nov 2006 Location: NS Canada Posts: 24,268	Quote: Originally Posted by Raven18940 See, this is the disconnect here. Because if I read the specs right SAE 90 should be a minimum of 13.5, not 19.5. So how do you know they meant 110 when they said 90? Maybe they meant 90? The MX-5 isn't exactly a torque monster. If you were to ask over in the lubrication section you might get more answers. Whether or not they'll agree with what's been recently said, I have no idea, but it will make an interesting read. __________________ 2007 Copper Red NC GT PRHT 6AT; 2011 Ranger XLT AT Supercab 4x4;  2007 Bombardier RXP fluid drive; 2012 Renegade Sport 600 Ace with CVT.

24th January 2011, 09:33	#20
Lance Schall Supporting Member Join Date: Nov 1999 Location: Jerome, AZ Posts: 21,297	Quote: Originally Posted by RubyDoo S2KPuddyDad is a specialist in rear ends, ... So his post here is the authoritative final word. Except I'd use something in the 75W-90 range, a GL-5, run it to 30,000 miles before changing it, and there is nothing special about Amsoil. Other than that, he's spot on.  __________________ Original owner of 291,192 mile 1990 Miata | Indian Turquoise re-spray | '92 crankshaft | '94 pulley | 6 speed | 4.300 Torsen II | FM radiator | FM exhaust | GAB | Millen springs and bars | Robbins |
24th January 2011, 10:53	#21
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	Since 2006 75/90W in general (check your brand of use for there tech info) is no longer meeting the minimum safe operating standards for the differential. This is not my doing or is it because I say so.....IT IS FACT BY YOUR MANUFACTURER AND BY THE OIL INDUSTRY AT LARGE. You can continue to use 75/90W and find no notable effect or issue but you take that chance.  Be an informed consumer check the brand of oil that you use web site. Check the numbers (all of them that concern your use) then at that point you will know if the brand and type/blend of oil in question is the right oil for your needs.  Please adjust your thinking.......This is what the oil people want you to do! 75/110W is now the Minimum safe oil to use if your gear box required 75/90W You guys do as you please you have been informed and given good information not opinion __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver

24th January 2011, 11:05	#22
Raven18940 Third gear Join Date: Nov 2010 Location: Greater DC Area Posts: 413	Quote: Originally Posted by S2KPuddyDad Most 75/ 90w will fall below 13.5 this number is not a safe minimum. Standards are 19.5 for your Miata differential. The Miata diff case only holds about 900ML of fluid not much for a lot of heat and shear going on inside our differential. If you need more reassurance please do more research on your computer or just use what you think is best....Good luck See, I use synthetic oil so I'm not worried about the oil not being the viscosity that it's supposed to be. Mobil 1 is pretty on the ball with such things.  Now you say that 19.5 cSt is the spec, which is fine by me, but how do you know this? Where did 19.5 come from? __________________ Currently miataless 2011 Mazda 2
24th January 2011, 11:52	#23
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	Quote: Originally Posted by Raven18940 See, I use synthetic oil so I'm not worried about the oil not being the viscosity that it's supposed to be. Mobil 1 is pretty on the ball with such things.  Now you say that 19.5 cSt is the spec, which is fine by me, but how do you know this? Where did 19.5 come from? synthetic or standard oil makes no difference the numbers are the numbers. Please check the manufactures specs and minimums of the blend you use. The number is the standard for this type of gear box. I can't keep posting it is getting redundant. At this point please others chime in with fact not opinion. All that are in question about the brand oli and blend they use check your manufactures spects and minimums or if you have no time for this debate just use 75/110W again it's a no brainer __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver

24th January 2011, 11:56	#24
wooo Wheels flew off Join Date: Nov 2006 Location: NS Canada Posts: 24,268	Quote: Originally Posted by S2KPuddyDad ... The number is the standard for this type of gear box.... Where can we find that? Supporting documents?? Quote: I can't keep posting it is getting redundant You keep asserting the 19.5 number, but don't tell us where to check that.  __________________ 2007 Copper Red NC GT PRHT 6AT; 2011 Ranger XLT AT Supercab 4x4;  2007 Bombardier RXP fluid drive; 2012 Renegade Sport 600 Ace with CVT.
24th January 2011, 13:54	#25
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	Quote: Originally Posted by wooo Where can we find that? Supporting documents?? You keep asserting the 19.5 number, but don't tell us where to check that.  I don't mean to be short or be none informative about a question. I called Honda a few years back and asked. You can call Mazda and do the same. The Mazda, Honda, KIA along with others use the Mazda 3rd member design.  The oil manufacturing industry it putting the information out to all auto manufactures the changes in oil ratings. Everything is changing Toyota now uses a straight weight engine oil in all new autos and trucks being made now. The hypoide gear box has not changed but oil has we all must keep up. __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver

24th January 2011, 14:35	#26
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	When I get time I will call Richmond and a few others to ask what there minimum and maximums are. I know Richmond gear company recommends 75/140 for all their hypoid gears they make. __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver
24th January 2011, 15:46	#27
Raven18940 Third gear Join Date: Nov 2010 Location: Greater DC Area Posts: 413	Does Richmond make the stock rear? __________________ Currently miataless 2011 Mazda 2
24th January 2011, 17:32	#28
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	Quote: Originally Posted by Raven18940 Does Richmond make the stock rear? No, but they do make 7" hypoid gears that fit our 3 rd member. __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver

24th January 2011, 18:18	#29
wooo Wheels flew off Join Date: Nov 2006 Location: NS Canada Posts: 24,268	Quote: Originally Posted by S2KPuddyDad I don't mean to be short or be none informative about a question. .... So basically you don't know what Mazda recommends for the NC's diff. That 19.5 business was just made up. __________________ 2007 Copper Red NC GT PRHT 6AT; 2011 Ranger XLT AT Supercab 4x4;  2007 Bombardier RXP fluid drive; 2012 Renegade Sport 600 Ace with CVT.
24th January 2011, 18:48	#30
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	Quote: Originally Posted by wooo So basically you don't know what Mazda recommends for the NC's diff. That 19.5 business was just made up. Wow....the Mazda rear is the same as the Honda the number is Honda and will translate to Mazda as it is the same. This is just not our rear it is the type of gear box in general. I don't get it, it is explained in the TSB I posted. I don't make this crap up I'm not educated at this level. You take the information your given and you pass it along. Don't shoot the messenger..... The TSB states that MOST 75/90 oils will fall below Industry standards for minimum protection. For me and my 25k investment I will take the information and use the 75/110 as the oil companies tell me. __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver

24th January 2011, 18:54	#31
wooo Wheels flew off Join Date: Nov 2006 Location: NS Canada Posts: 24,268	Quote: Originally Posted by S2KPuddyDad ...I don't get it, it is explained in the TSB I posted. .... TSB? Which of your posts contains this TSB? Whose TSB is it? Is it a Mazda TSB? __________________ 2007 Copper Red NC GT PRHT 6AT; 2011 Ranger XLT AT Supercab 4x4;  2007 Bombardier RXP fluid drive; 2012 Renegade Sport 600 Ace with CVT.
24th January 2011, 19:04	#32
wooo Wheels flew off Join Date: Nov 2006 Location: NS Canada Posts: 24,268	It appears that the OMs and WSMs for NCs of all years recommend 75W-90 or 80W-90 for the diff. Is Mazda wrong in this, or out of date? Surely if Mazda thought 75W-110 was required they would have said so. Is Mobil wrong in saying that their Synthetic 75W-90 is suitable for differentials? This is puzzling. __________________ 2007 Copper Red NC GT PRHT 6AT; 2011 Ranger XLT AT Supercab 4x4;  2007 Bombardier RXP fluid drive; 2012 Renegade Sport 600 Ace with CVT.

24th January 2011, 19:20	#33
arejohn Fourth gear Join Date: Oct 2007 Location: Durham, NC Posts: 1,420	Unable to locate the 110 stuff I decided to go with Castro Synthetic GL5. Impressed by the spec sheet approvals. Its a 15 that I will live with. http://www.castrol.com/liveassets/bp...CANTS_3750.pdf __________________ Copper Red Touring.
24th January 2011, 19:28	#34
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	Quote: Originally Posted by wooo It appears that the OMs and WSMs for NCs of all years recommend 75W-90 or 80W-90 for the diff. Is Mazda wrong in this, or out of date? Surely if Mazda thought 75W-110 was required they would have said so. Is Mobil wrong in saying that their Synthetic 75W-90 is suitable for differentials? This is puzzling. I call it a TSB because it reads as such.... Our owners book says SAE 90w or 80/90w (75/90* not available from Mazda) The oil companies changed ratings to better narrow the range of use and to bring it all under a global standard as I understand it. The 75/110 is more in line and in the range of standard use now.  75/140 for trucks SUV and towing and SAE190 SAE250 for sever use. Take note to your auto parts stores gear oil selections….Before it was 90w or 75/90 now you have up to a half dozed blends to chose from. Here is more about it, http://www.lubrizol.com/DrivelineAdd...arOil/GL5.html __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver

24th January 2011, 20:01	#35
Raven18940 Third gear Join Date: Nov 2010 Location: Greater DC Area Posts: 413	Actually I just sawy 75W90, 80w90, and a few 75W140. __________________ Currently miataless 2011 Mazda 2
24th January 2011, 20:42	#36
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	I'm sorry you did not find more. Here is more info on oil via the manufactures  http://www.mobil.com/USA-English/Lub...LS_75W-90.aspx Amsoil touches on the subject here http://synthetic-motor-oil-air-filte...0-gear-oil.htm __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver

24th January 2011, 20:51	#37
RubyDoo Supporting Member Join Date: Nov 2009 Location: Driftless Zone Posts: 10,581	Quote: Originally Posted by wooo So basically you don't know what Mazda recommends for the NC's diff. That 19.5 business was just made up. Quote: Originally Posted by wooo It appears that the OMs and WSMs for NCs of all years recommend 75W-90 or 80W-90 for the diff. Is Mazda wrong in this, or out of date? Surely if Mazda thought 75W-110 was required they would have said so. Remember that this is the same Mazda that recommended GL4 OR GL5 for the tranny (do they still?), even though many of us have discovered that GL5 is problematic for the syncros and the GL4 Motorcraft cleans up a GL5 problem in time. __________________ When something goes wrong, I'm the first to admit it and the last one to know.  ~Paul Simon
24th January 2011, 21:27	#38
wooo Wheels flew off Join Date: Nov 2006 Location: NS Canada Posts: 24,268	Quote: Originally Posted by RubyDoo Remember that this is the same Mazda that recommended GL4 OR GL5 for the tranny (do they still?), even though many of us have discovered that GL5 is problematic for the syncros and the GL4 Motorcraft cleans up a GL5 problem in time. At this point I don't have an opinion on the matter. I am just trying to gather facts on which to base an opinion. I'm not getting an answer on why Mazda is still recommending 75W-90, well after the GL5 spec was revised and new categories created. S2K seems to be saying that an oil with 15 cSt is too thin to be used in diffs, yet he then points us to the Mobil 75W-90 spec sheet.  Quote: •Mobil 1 Synthetic Gear Lubricant LS 75W-90 is SUITABLE for use in modern high performance automobiles like SUV's, Vans and Light duty trucks requiring API GL-5 level performance •Mobil 1 Synthetic gear Lubricant LS 75W-90 is intended for initial fill, topping-off or refilling differentials, He may very well be correct in suggesting a heavier oil for the diff but he's doing a poor job of convincing me of that. Not getting answers to asked questions isn't helping. As I said previously, puzzling. Too bad this isn't in the lube section where the tribologists hang out, and could chime in on this matter. __________________ 2007 Copper Red NC GT PRHT 6AT; 2011 Ranger XLT AT Supercab 4x4;  2007 Bombardier RXP fluid drive; 2012 Renegade Sport 600 Ace with CVT.

24th January 2011, 22:28	#39
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	I posted Mobil 1 specs for you to see not to recommend. I also posted Amsoil to compare with some explanation of the range of theses blends.  I have not evaded your question(s) I think I answered them to the best of my ability and recollection. I never talked or Emailed the engineers at Mazda I did talk to customer service at Honda motor Co USA some years ago and was given a range of 19 to 32 cst as a safe range for general use of the S2000 Differential. I was told to use SAE90W as per my S2000 owners manual. Maybe the person I talked to was wrong I don’t know??? Honda dealers never sold and Honda motor Co never made a differential oil for the S2000. There are countless horror stories of the dealers using Honda CRV transaxle fluid in S2000 rears. The owner did not get down the road far before the rear would fail.  My S2000 manual does not give any other oil choice but GL-5 SAE90W The oil companies are putting this out there for us to know that you have better choices. They are telling us that 75/110 will protect our investment better with out compromise. __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver
24th January 2011, 23:15	#40
Bimmer Second gear Join Date: Apr 2010 Location: Germany Posts: 270	Quote: Originally Posted by wooo At this point I don't have an opinion on the matter. I am just trying to gather facts on which to base an opinion. I'm not getting an answer on why Mazda is still recommending 75W-90, well after the GL5 spec was revised and new categories created. He may very well be correct in suggesting a heavier oil for the diff but he's doing a poor job of convincing me of that. +1  I was thoroughly confused by this thread, and a bit concerned, because I just replaced all the differential and transmission oils in my two Subarus with 75w90 because that's what's specified.  (Don't even ask why a guy called Bimmer on a Miata site has two Subarus.)  So, I went to BITOG and found this: Before 2001 or so these are the grade ranges of 90 and 140 90: 13.5cSt to <24cSt at 100C (212F) 140: 24cSt to <41cSt at 100C Now: 90: 13.5cSt to <18.5cSt at 100C 110: 18.5cSt to <24cSt at 100C 140: 24cSt to <32.5cSt at 100C 190: 32.5cSt to <41cSt at 100C FWIW, this is from a thread on BITOG titled "Ford switch 80w-90 to 75w-140 synthetic." Of course, Ford made that switch in 2001 or so... Also, see this:  http://www.lubrizol.com/DrivelineAdd...fications.html I still have no idea where Puddy's 19.5cSt number came from, but the MAXIMUM viscosity for 90-weight oil seems to be 18.5cSt @ 100c, so if Honda really spec'ed a 19.5cSt, then that would indeed be a 110-weight oil.  Otherwise, if since '01 (or better, since the NC appeared in '05) Mazda says 75w90, then they presumably mean 75w90, not 75w110 or anything else.  And I just checked, and the Redline 75w90NS I put in my transmission has a viscosity of 15.6cSt, and the Redline 75w90 for the differentials is 16.4. I'll sleep well tonight! YMMV, Bimmer

24th January 2011, 23:44	#41
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	Quote: Originally Posted by Bimmer Also, see this:  http://www.lubrizol.com/DrivelineAdd...fications.html I still have no idea where Puddy's 19.5cSt number came from... the maximum viscosity for 90-weight oil seems to be 18.5cSt @ 100c. Bimmer customer service at Honda motor Co USA some years ago and was given a range of 19 to 32 cst as a safe range for general use of the S2000 Differential. I was told to use SAE90W as per my S2000 owners manual. Maybe the person I talked to was wrong I don’t know??? I also stated that some not all brands fall below standards. I said it would be best to check your brand of choice specs. Red Line has a high number it is one of the better brands to use as is Amsoil. I am not an oil guy I just read that the 75/110 is a better choice and covers a better range. I told my self never get into a oil thread on line you will always find strong opinion that can escalate into hard debate or hard feelings. I don’t want anyone to be angry with me over what I was told via a phone call 4+ years ago, I am thinking this information was wrong.  I do not know everything about oil. I only know what I was told and what I read and use this information as what I think best for me. Seeing the numbers I still feel that the 75/110 is the better choice. __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver
25th January 2011, 00:15	#42
Bimmer Second gear Join Date: Apr 2010 Location: Germany Posts: 270	Quote: Originally Posted by S2KPuddyDad customer service at Honda motor Co USA some years ago and was given a range of 19 to 32 cst as a safe range for general use of the S2000 Differential. This sounds like the old 140 weight spec... Quote: Originally Posted by S2KPuddyDad I also stated that some not all brands fall below standards. I said it would be best to check your brand of choice specs. I doubt that any name brand oil does NOT meet standards. Even if they did, I doubt that they would pubicize specs that didn't meet standards.  Quote: Originally Posted by S2KPuddyDad I am not an oil guy I just read that the 75/110 is a better choice and covers a better range...  Seeing the numbers I still feel that the 75/110 is the better choice. I'm not trying to bust your chops. I've seen your other posts, and the only reason I would NOT send a differential to you would be if I could find somebody out here on the Left Coast who could do it... I'm just trying to make sure I'm using the right gear oil.  FWIW, I doubt that using 110 weight instead of 90 weight oil would make much difference (maybe a slight loss of power and efficiency).

25th January 2011, 00:38	#43
arejohn Fourth gear Join Date: Oct 2007 Location: Durham, NC Posts: 1,420	I have done a lot of reading as a result of this thread and have come to the conclusion that 75-110 is a better choice than 75w-90 and should be my first choice for my next differential change but this time I am going with Castrol 75w90. I should mention that my differential was recently replaced for a whine at 50 and 70mph. __________________ Copper Red Touring.
25th January 2011, 06:49	#44
Raven18940 Third gear Join Date: Nov 2010 Location: Greater DC Area Posts: 413	Quote: Originally Posted by S2KPuddyDad I told my self never get into a oil thread on line you will always find strong opinion that can escalate into hard debate or hard feelings. I don’t want anyone to be angry with me over what I was told via a phone call 4+ years ago, I am thinking this information was wrong.  I do not know everything about oil. I only know what I was told and what I read and use this information as what I think best for me. Seeing the numbers I still feel that the 75/110 is the better choice. No one is attacking you or angry with you. You were just a bit adamant that 19.5 was the correct number and we had no idea where it had come from.  But since that number came from a phone call to Honda, I'll just try emailing Mazda with a very specific question and hopefully it'll get bumped to a lubrication engineer who understands what I'm asking. If that doesn't work I'll just drain the oil and have the viscosity tested.  As an aside to those that want to use 75W-110, but would prefer Mobil 1, mix 75W-90 and 75W-140 in equal parts and you should have a nice 75W-110.  __________________ Currently miataless 2011 Mazda 2

25th January 2011, 07:46	#45
wooo Wheels flew off Join Date: Nov 2006 Location: NS Canada Posts: 24,268	Quote: Originally Posted by S2KPuddyDad ... I have not evaded your question(s) I think I answered them to the best of my ability and recollection. ... I don't see any answer to this: Quote: Whose TSB is it? Is it a Mazda TSB? Way back you said: Quote: Since our rear requires a SAE 90W you need a cst of 19.5 How can that be true since we now know that the standard for 90 weight ( since 2001?) is 13.5 to 18.5 cSt? __________________ 2007 Copper Red NC GT PRHT 6AT; 2011 Ranger XLT AT Supercab 4x4;  2007 Bombardier RXP fluid drive; 2012 Renegade Sport 600 Ace with CVT.
25th January 2011, 07:51	#46
wooo Wheels flew off Join Date: Nov 2006 Location: NS Canada Posts: 24,268	Quote: Originally Posted by S2KPuddyDad ... I also stated that some not all brands fall below standards. .... Please give an example of just one diff oil that falls below "standards"? And you might explain what you mean by standards in this context. I suspect you are saying that 75W-90 oils don't meet the 19.5 cSt number that you have declared a standard. But daaahhh the SAE spec "standard" for 75W-90 tops out at 18.5 cSt. __________________ 2007 Copper Red NC GT PRHT 6AT; 2011 Ranger XLT AT Supercab 4x4;  2007 Bombardier RXP fluid drive; 2012 Renegade Sport 600 Ace with CVT.

25th January 2011, 07:58	#47
wooo Wheels flew off Join Date: Nov 2006 Location: NS Canada Posts: 24,268	Quote: Originally Posted by S2KPuddyDad ... The oil companies are putting this out there for us to know that you have better choices. .... What oil companies are putting "this" out there? You haven't told us that, you didn't say who authored that so called TSB. I suspect the answer is Amsoil. What manufacturers are actually making/selling 75W-90? All I have found so far is Amsoil and a couple of other boutiques. What about any of the large manufacturers. You seem to have a tendency to exaggerate, as in a few becomes all, a phone call becomes a standard. This doesn't help your credibility.  __________________ 2007 Copper Red NC GT PRHT 6AT; 2011 Ranger XLT AT Supercab 4x4;  2007 Bombardier RXP fluid drive; 2012 Renegade Sport 600 Ace with CVT.
25th January 2011, 08:23	#48
S2KPuddyDad Second gear Join Date: Jul 2009 Location: Florida Posts: 173	I have admitted I may have/was misinformed I also admit I do not know enough about oil to hang with you in this thread.  I will continue to use 75/110 as it has a wider range of protection. __________________ 2010 True Red "mx-5" touring PRHT with sport suspension and LSD,  2002 Suzuka Blue Honda S2000 2011 fj 4x4 daily driver

25th January 2011, 08:29	#49
Raven18940 Third gear Join Date: Nov 2010 Location: Greater DC Area Posts: 413	Just read the manual for myself. It specifies the following grades as acceptable for the rear: API GL-5 of viscosity SAE 90, 80W-90, or 75W-90. Unless Mazda gets back to me with a specific number, these are the specs I will follow. Quote: Originally Posted by S2KPuddyDad I will continue to use 75/110 as it has a wider range of protection. Thicker does not necessarily mean more protection. __________________ Currently miataless 2011 Mazda 2
25th January 2011, 08:43	#50
mx5mia Sixth Gear Join Date: Mar 2006 Location: S-East, PA. PACE Miata Club Posts: 5,931	Quote: Originally Posted by Bimmer And I just checked, and the Redline 75w90NS I put in my transmission has a viscosity of 15.6cSt, and the Redline 75w90 for the differentials is 16.4. I'll sleep well tonight! Bimmer Bimmer,.. Thanks for the numbers on the Redline 75w-90. I have that in my diff now, so I feel better about that reading the above. But I wanted to comment on the 75w-90NS you have in the tranny. I first tried that in my previous 02 Miata 5spd and was not happy with it. It was a little better than the "dino" lube, but still not good. I called and spoke with Dave at Redline, and he explained "why". Dave told me the 75w-90NS is a compromise lube. It has some anti slip agents in it to help the snychros grip, but it also has some slip agents in it to help ring and pinion gears to slip. This is a compromise lube for TRANSAXLES. He did not recommend it for a separate manual transmission. I then drained it out of my tranny and installed the Redline "MT-90", 75w-90 fluid. After the lube washed the slip agents off of the snychros, it made a big difference in the smoothness of the shifting. I loved it! So if you are using the 75w-90NS in a transaxle, then you are OK. But I was a lot happier with the MT-90 in that 5 spd Manual Transmission. Just a FWIW,.... __________________ 06 Winning Blue GT, aka Mxie; 6mt, Sport Susp Pkg, Prem Pkg 2, X-Pel Clr Bra, Wolo Air Horn, RoadsterSport Q & Mid-Pipe, RX8 Red/Yellow Sways, & Kansai FST Brace. 2006 Winning Blue Registry Link

25th January 2011, 08:59	#51
wooo Wheels flew off Join Date: Nov 2006 Location: NS Canada Posts: 24,269	If you Google 75W-110 most of the responses are from forums discussing the topic, and Amsoil blurbs. Here is a link to Amsoil: http://www.amsoil.com/storefront/svt.aspx Quote: ... AMSOIL SEVERE GEAR® (75W-110) provides superior performance and replaces competitors’ 75W-110, 75W- 90 and 80W-90 gear oils. It delivers better viscosity protection than SEVERE GEAR 75W-90 and better fuel efficiency than SEVERE GEAR 75W-140. ... So what do we know, or think we know, the known knowns? - The 75W-90 spec was split in two, and the 110 took the high end. - Mazda continues to recommend the new 90 for the NC. - I can't find much in the way of car makers recommending the 110. - I can't find any top tier lubricant makers selling a 110. - Amsoil is all for the 110. - I don't see any big downside to using the 110, but is there any advantage? - We each will have to make our own decision until a trusted tribologist tells us what to do. __________________ 2007 Copper Red NC GT PRHT 6AT; 2011 Ranger XLT AT Supercab 4x4;  2007 Bombardier RXP fluid drive; 2012 Renegade Sport 600 Ace with CVT.
25th January 2011, 09:30	#52
aemericas Third gear Join Date: Aug 2008 Location: Austin, Texas Posts: 431	I think I understand where the cSt=19.5 may have come from. The range for 90W is 14-25. If you average that you get 19.5.  Is that just lucky math? __________________ 2006 MX-5 Galaxy Grey 5MT Robbins Canvas Top RX-8 Sway Bars, Racing Beat Springs, Tokico HTS, Cobalt FSTB, RoadsterSport II
25th January 2011, 09:34	#53
wooo Wheels flew off Join Date: Nov 2006 Location: NS Canada Posts: 24,269	Quote: Originally Posted by aemericas ... The range for 90W is 14-25. ... Isn't that is a was? 19.5 is conveniently close, but not too, to Amsoil's 20.3 for it's 75W-110.  __________________ 2007 Copper Red NC GT PRHT 6AT; 2011 Ranger XLT AT Supercab 4x4;  2007 Bombardier RXP fluid drive; 2012 Renegade Sport 600 Ace with CVT.

25th January 2011, 11:32	#54
Raven18940 Third gear Join Date: Nov 2010 Location: Greater DC Area Posts: 413	So I just heard back from Mazda...they referred me to page 8-18 of the manual. Yup, they referred me to the page on engine oil for my differential oil question.  __________________ Currently miataless 2011 Mazda 2
25th January 2011, 12:21	#55
aemericas Third gear Join Date: Aug 2008 Location: Austin, Texas Posts: 431	Quote: Originally Posted by wooo Isn't that is a was? 19.5 is conveniently close, but not too, to Amsoil's 20.3 for it's 75W-110 Yes, I should have said "was". The information available is confusing, but what I've been able to find is that the old 90W had a range of 13.5-24 (average 19.5). In 2006 sae j306 changed to narrow the range of 90W to 13.5-18.5 and added 110W 18.5-24 cSt.  http://www.lubrizol.com/J306.aspx?id=33216&terms=J306 An interesting quote (which has the 19.5 value) from that page Quote: For example, under the old classifications, if the optimum 100°C viscosity for an axle was 19.5 cSt, the OEM would normally specify an SAE 90 lubricant. Sooooo, Amsoil's 75W-110 falls in the range of the "old" 90W and would appear to be a good selection assuming that Mazda's recommendations were based on the old 90W standard.  Given that I have an 06 which was actually built in 05 and probably designed before that, what are the chances that my Owner's manual was referring to the old SAE J306 standard or the revised 2006 version? __________________ 2006 MX-5 Galaxy Grey 5MT Robbins Canvas Top RX-8 Sway Bars, Racing Beat Springs, Tokico HTS, Cobalt FSTB, RoadsterSport II

25th January 2011, 12:36	#56
Raven18940 Third gear Join Date: Nov 2010 Location: Greater DC Area Posts: 413	Quote: Originally Posted by aemericas Given that I have an 06 which was actually built in 05 and probably designed before that, what are the chances that my Owner's manual was referring to the old SAE J306 standard or the revised 2006 version? Well you could go by my 2010 manual which still specs SAE 90 oil. __________________ Currently miataless 2011 Mazda 2
25th January 2011, 13:03	#57
aemericas Third gear Join Date: Aug 2008 Location: Austin, Texas Posts: 431	Quote: Originally Posted by Raven18940 Well you could go by my 2010 manual which still specs SAE 90 oil. Even the Amsoil website lists 80W-90 and 75W-90 as recommended. It does list 75W-110 too. __________________ 2006 MX-5 Galaxy Grey 5MT Robbins Canvas Top RX-8 Sway Bars, Racing Beat Springs, Tokico HTS, Cobalt FSTB, RoadsterSport II

25th January 2011, 13:05	#58
cheetahdriver Fifth gear Join Date: Oct 2001 Location: springdale, ar *04MSM, 02LS* Posts: 3,323	well, sort of, but not so much.... Quote: Originally Posted by S2KPuddyDad Since our rear requires a SAE 90W you need a cst of 19.5 This is why the change and why the old 75/90 is the new 75/110 You need to use 75/110 Also note your owners manual states no 75/90 available through Mazda for your differential  SAE 90W or 80/90W as a second 2 main reasons for diff failure is driver error and inadequate lubrication while the 19.5cSt number you are getting is right in the middle of the pre-revision 90wt range, it does not necessarily mean that you need a 19.5cSt lubricant to adequately lubricate a miata diff.  the old range for 90wt was 13.5-23.9. since the miata diff specs were done during this period, it is safe to assume that a 13.6cSt lubricant will do the job. most of the XXw90 and straight 90wt lubricants are all formulated toward the light end of the scale (one of the very reasons that the revision took place). since the current miata still specs a 90wt, i am fairly certain that you don't need a 19.5, or a 22cSt oil to adequately lubricate the rear end. as most people have been using a 13.5-15cSt lubricant all along, and there have been no rash of diff failures, i would be happy to call that empirical proof and move on.  a heavier lubricant in the rear end will just make it run hotter, and use more fuel.  for those interested in the mechanics of it, a very good table that i have posted before is http://www.lubrizol.com/DrivelineAdd...fications.html <edit> well, there was a whole 'nuther page showed up while i was posting this (and taking calls). i see most got there while i was typing<G>
25th January 2011, 13:07	#59
tom4416 Moderator Join Date: Nov 2005 Location: Southern Maryland Posts: 22,801	Since changing the differential oil was on my to do list for today and I've been reading this thread, I stopped at the dealer before picking up lubricant. The service manager (who I have a fair amount of respect for), looked at a couple of factory books, looked online (at what I don't know) and said that the recommendation is as printed in the owners manual of my 08. He then pointed to a 55 gallon drum of Castrol 80/90 which is what they use for a rear differential change, and then pointed to a 55 gallon drum of something else from Mazda which is for front wheel drive systems only. That was good enough for me, bought a quart of Castrol 80/90 from the dealership and will put that in there and drive with peace of mind. Now, I have an automatic so no LSD so others may benefit more form something else. __________________ Tom 1 of 1 91 Sunburst, 93LE, 94 Laguna Blue R,  http://www.cardomain.com/ride/2281248/1

25th January 2011, 15:07	#60
Raven18940 Third gear Join Date: Nov 2010 Location: Greater DC Area Posts: 413	Quote: Originally Posted by cheetahdriver the old range for 90wt was 13.5-23.9. since the miata diff specs were done during this period, it is safe to assume that a 13.6cSt lubricant will do the job. most of the XXw90 and straight 90wt lubricants are all formulated toward the light end of the scale (one of the very reasons that the revision took place). since the current miata still specs a 90wt, i am fairly certain that you don't need a 19.5, or a 22cSt oil to adequately lubricate the rear end. as most people have been using a 13.5-15cSt lubricant all along, and there have been no rash of diff failures, i would be happy to call that empirical proof and move on. Welcome to the flaw in the argument I pointed out two pages ago.  __________________ Currently miataless 2011 Mazda 2
25th January 2011, 15:14	#61
Jim Boemler Sixth Gear Join Date: Dec 2006 Location: Mukilteo WA Posts: 8,343	If the notion of trading a little gas mileage for more diff protection bothers you, by all means buy the 90. If the notion of trading a little diff protection for some gas mileage bothers you, buy the 110 (or even 140). Like most things in life, it's a trade-off -- neither decision is right or wrong. jim (tired of a simple decision becoming a running gunfight... ) __________________ "Speed limits are like herpes" -- Jeremy Clarkson '06 GG Coupe, JIC suspension, extra rubber, Cosworth SC finally installed! '92 Spec Miata #30

25th January 2011, 15:21	#62
Raven18940 Third gear Join Date: Nov 2010 Location: Greater DC Area Posts: 413	Quote: Originally Posted by Jim Boemler If the notion of trading a little gas mileage for more diff protection bothers you, by all means buy the 90. If the notion of trading a little diff protection for some gas mileage bothers you, buy the 110 (or even 140). Like most things in life, it's a trade-off -- neither decision is right or wrong. jim (tired of a simple decision becoming a running gunfight... ) The annoying thing about this argument is that neither side really has any data. Neither side has any used oil analysis to prove that either oil is better or worse. It really boils down to one question, do you think you're more clever than the engineer who designed the car? __________________ Currently miataless 2011 Mazda 2
25th January 2011, 17:10	#63
Jim Boemler Sixth Gear Join Date: Dec 2006 Location: Mukilteo WA Posts: 8,343	Not quite, Raven. The question is "Do you have the same priorities as the manufacturer?" It's not that you or they "know more". The manufacturer has a lot of criteria that you don't -- cost, emissions, mileage, corporate partnerships, etc. It's legitimate to think of the manufacturers recommendations as "minimums", and sometimes they're even better than minimum, but their goal isn't to recommend "the best" for you -- that's your job. jim __________________ "Speed limits are like herpes" -- Jeremy Clarkson '06 GG Coupe, JIC suspension, extra rubber, Cosworth SC finally installed! '92 Spec Miata #30

25th January 2011, 17:31	#64
WHY! Supporting Member Join Date: May 2009 Location: CT Posts: 5,375	Well said JB. The great thing is that no one can make anyone else put anything in their car.  Follow the owner's manual. Don't change it all. Drain it, run it through a coffee filter and put it back. Whatever puts a shine on your armor. You can follow the advice of the butcher, the baker or the candlestick maker.  Me personally? I'd follow the advice of the guy who builds rearends for a living. __________________ http://www.flickr.com/photos/jamesmx5
25th January 2011, 19:40	#65
Bimmer Second gear Join Date: Apr 2010 Location: Germany Posts: 270	Quote: Originally Posted by mx5mia Bimmer... I wanted to comment on the 75w-90NS you have in the tranny.  So if you are using the 75w-90NS in a transaxle, then you are OK... I'm afraid that this wasn't for a Miata, it was for my '02 Subaru Impreza (I think I mentioned this above somewhere). FWIW, Redline's 75w90NS (and one quart of the Redline's Lightweight Shockproof "Smurf Blood") is highly praised on the Subaru forums for the manual transaxles, and it made shifting much easier in my car.

25th January 2011, 19:47	#66
cheetahdriver Fifth gear Join Date: Oct 2001 Location: springdale, ar *04MSM, 02LS* Posts: 3,323	well... Quote: Originally Posted by Raven18940 The annoying thing about this argument is that neither side really has any data. Neither side has any used oil analysis to prove that either oil is better or worse. It really boils down to one question, do you think you're more clever than the engineer who designed the car? i have one, just haven't sent it in yet, 60k on my 02LS. hopefully go out in the mail this week to blackstone.
25th January 2011, 20:02	#67
Bimmer Second gear Join Date: Apr 2010 Location: Germany Posts: 270	Quote: Originally Posted by Raven18940 Neither side has any used oil analysis to prove that either oil is better or worse. It wouldn't really prove anything if we did, either... You'd need dozens is not hundreds of UOAs to come up with statistically significant conclusions.  If you're trying to decide between 75w90 and 75w110, then the margins of errors on UOAs are too big, and the other variables like manufacturing tolerances in differentials, different brands of oil, and different driving styles, are virtually insurmountable.  For example, Driver A's differential might show a lot more wear than Driver B's, even if they use the same oil.  Or a sample of Brand A 75w90 after 30,000 miles might show a lot less wear than a sample of Brand B 75w90.  Or a sample from a differential made on a Monday might show a lot more wear elements than a differential made on a Tuesday, even if everything else (weight and brand of oil, driving style) were the exactly the same.  Or you could send the same exact sample to several labs and have results that vary 10-20%. Really.  So, pick whatever you guess will work best. Or do whatever your brother-in-law recommends (or the opposite). Or whatever Mazda says. Or whatever Puddy says. Or whatever Amsoil says. I don't know...