I pulled this together for a VW TDI forum. Last update was Oct '07. Most data comes from manufacturer spec sheets, but has been validated and/or expanded with oil analysis. Sorry...it's heavily weighted to Euro and VW fluids.
There's been a steady shift from 80-90 gear lubes to fluids that are basically automatic transmission fluid with some extreme pressure additives in order to improve corporate average fuel economy...so manufacturers can sell more trucks... You can see that the lightest fluids are off the chart...
When it comes to improving fuel economy thru changing fluids, the differential is the largest factor, with tranny second and engine last.
Changing from petroleum to synthetic - even with the same viscosity - can make a significant difference. For example - a class 8 truck (semi) tractor with dual drive axles, when moving from petroleum fluids to real synthetics, can gain 8.3%. 5.25% is the differentials, about .5% is the engine.
I did some highway testing with my old VW diesel - moving from the factory 75W-90 synthetic, to a synthetic synchromesh fluid, down to VW G52, and back up. The move from 75W-90 to the really thin G52 was worth 1.8mpg. In the end I moved back to 75W-90 to keep my 390,000 mile transmission a bit happier.
VI is viscosity index and speaks to viscosity stability as temperatures change. Higher is more resistant to change with temperature.
Transmission fluid viscosity is normally rated at 40C, while engine oils are rated at 100C. And, as already pointed out, the viscosity scales for gear oil and engine oils are different.
Viscosities are in cSt - centistokes - and are essentially a timed flow thru a cup with a hole in it.
(Manual Tranny Fluids)
VI Vis@40C Vis@100C
128 159.0 18.3 = AMSOIL CTL SAE 50 Powershift GL-1
..............16.7 = Motul MOTYLGEAR 75-90 GL-4/-5
..............15.6 = VW G50/G51 GL-4
185 90.0 15.6 = Redline MT-90 75-90 GL-4
..............15.2 = Mobil 1 Synthetic 75W-90 GL-5
..............15.2 = Motul Gear 300 75-90 GL-4/-5
..............15.0 = Elf Tranself Synthese FE 75-90 GL-4/-5
132 116.0 14.9 = AMSOIL AGL 80W-90 GL-5
177 84.5 14.7 = AMSOIL MTG 75-90 GL-4
..... 76.6 14.2 = VW G052-911
133 76.2 11.0 = AMSOIL CTJ SAE 30 Powershift GL-1
183 56.2 10.6 = Redline MTL 70-80 GL-4
194 47.1 9.6 = AMSOIL MTF Synchromesh Trans fluid (GM/Chrysler) GL-?
208 41.6 9.1 = Penzoil Synchromesh trans fluid GL-?
198 34.0 7.5 = Redline D4 ATF Dexron III / Mercon / API GL-4
138 40.5 7.1 = AMSOIL CTG SAE 10W Powershift GL-1
..... 31.2 6.5 = VW G-052-171-A2 GL-?
..... 35.1 6.4 = VW G-055-726-A2 GL-?
..............6.3 = VW G52 (part numbers G052726A2 / G05272601) GL-?
(Automatic Tranny Fluids - except for Redline D4 dual-use)
VI Vis@40C Vis@100C
.............8.3 = Honda CVT Fluid
.............7.6 = Mobil 1 Synthetic ATF
198 33.5 7.5 = Redline D4 ATF Dexron III / Mercon / API GL-4
.............7.4 = Mobil 1 Synthetic Dexron/Mercon
197 32.5 7.2 = Redline Synthetic ATF Dexron II / Mercon
.............7.1 = Mobil 1 Synthetic Multi-vehicle ATF
138 40.5 7.1 = AMSOIL Ford type F auto trans fluid
168 37.4 6.8 = AMSOIL Automatic Transmission Fluid ATF
..........5.5-6 = Ford Mercon SP
EVDRIVER wrote:THe point is about friction. Many automakers have the option of lower friction and higher quality synthetics but don't use them because of cost. Many EV converters change their gear oil to an appropriate better quality product designed for high rpm gear boxes and efficiency while not sacrificing protection. I would also wonder if the service manual call out different weight for various climates.
EVDRIVER wrote:Synthetic does not need the heat in cooler climates and the ice provides to thin and is more consistent. I used a very expensive gear oil in one of my EVs but I can't remember the brand. Anyone know the gear oil specs?
AndyH wrote:I don't have tech data for Nissan Matic S yet. I've purchased a quart and have sent a sample to an oil testing lab. I'll report back when I have numbers.
AndyH wrote:EVDRIVER wrote:THe point is about friction. Many automakers have the option of lower friction and higher quality synthetics but don't use them because of cost. Many EV converters change their gear oil to an appropriate better quality product designed for high rpm gear boxes and efficiency while not sacrificing protection. I would also wonder if the service manual call out different weight for various climates.
No. Nissan Matic Fluid S is supposed to be a synthetic fluid and is a lifetime fill. I'll know more when I get my lab report back.EVDRIVER wrote:Synthetic does not need the heat in cooler climates and the ice provides to thin and is more consistent. I used a very expensive gear oil in one of my EVs but I can't remember the brand. Anyone know the gear oil specs?AndyH wrote:I don't have tech data for Nissan Matic S yet. I've purchased a quart and have sent a sample to an oil testing lab. I'll report back when I have numbers.
EVDRIVER - I'm a reliability tech and have a business serving primarily commercial vehicle fleets - from cars/light trucks to class-8. I prefer long-life real synthetic fluids where they're best used, and recommend fluids and/or service intervals to improve reliability, service life, fuel economy when ever possible. Just so you know where I'm coming from.
Yes - friction is a factor. But...lubricants are a highly-engineered chemical mix. The traditional thought - as expressed by the unscientific testimonial you posted (sorry, truth) - is that a thicker fluid wastes more energy than a thinner fluid, and that must mean that thinner is better.
Two fluids otherwise identical in every way including viscosity can have different friction and/or energy saving properties with the addition of a friction modifier additive. (I'm not talking any over the counter product - I'm talking about chemistry tweaks in the oil formulation - never add anything to a fully formulated oil!).
Fluids must do more than one function. They lubricate, protect from rust and corrosion, transfer heat to the outer case of the transmission. Oil does not compress. A thin layer of oil on gear teeth, for example, forms the 'pillow' that keeps gear teeth from physically touching. Thinner fluids cannot protect from wear as well as a thicker fluid. Just one example.
Fluid choice includes a LOT of trade-offs.
For the Leaf - the gearbox uses Nissan's latest (and lightest) automatic transmission fluid. Don't change it to anything lighter (provided we can find anything thinner!) to chase economy - driving style and tire inflation will give us much larger performance gains with no potential down-side risk.
prberg wrote:I just wanted to follow up on the brake fluid maintenance requirement that was brought up earlier (obviously it's still bugging me).
I downloaded another Nissan maintenance schedule and I was surprised that I did not see the brake fluid change in that current maintenance schedule. I wonder why that is. I also noticed that the gasoline cars have the same maintenance schedule guidelines (schedule 1 or 2). I can understand why short trips are bad for gasoline cars. The engine warm up time, friction before fluids are circulated, etc. But I don't understand why short trips are so bad for EV's. Since I do drive a short ways to my job I guess I am in schedule 1 and still can't believe that we need to do annual brake fluid changes.
Why would the LEAF need this but not other Nissan cars? Did they use a different system that is not as air tight and can take on more moisture? Just bugging me that the LEAF has EXTRA maintenance that other Nissan's are not required to do. One of the big things with the LEAF was not having to do annual fluid changes, etc. Well I'll stop complaining now.
EVDRIVER wrote:Andy, I am well aware of the complexities and variables in fluids and their applications and even though you say "no" to my comment I never said the LEAF fluid was not the best application since I never stated I knew what it was and was wondering to see if there was a better option, no matter the viscosity or other merits. EV drives are also different than standard gear boxes as well. There are many EV builders that have done more detailed analysis on this I really did not see the need to go into technical detail on all the pros and cons since this is not a very tech forum and the point was simply to explore potential options and give some generic reasons why. I could also go into great detail for pages about parasitic loads in the drive, foaming, double-roling loads, details about all the regen misconceptions and other junk few would care to hear about or understand. Thank you for informing us about the exact fluid used in the LEAF, I don't think an chemical analysis is needed but some of these drives are shipped with fluids that can be upgraded to a worthwhile benefit with a quick check, not a lab analysis. It was simply something worth checking and I'm glad to looked it up on the LEAF specs for confirmation as I did not download that PDF, thank you.
wgs1912 wrote:Andy just for referance matic S is a new fluid for nissan. It's first use was in the 2009 370Z when it came out.