Switch diff/transfer case to synthetic...gas mileage increase?
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Redline say 6% achievable and I know there are documented trucks here seeing definite improvements. My Outback improved over the OEM stuff.
I switched the front & rear diffs and transfer case to Mobil 1 synthetic fluids on my 98 chevy 4x4 and did not notice any MPG increase and I've been keeping fuel mileage records on every tank of gas since this truck was new.
Wayne
Wayne
I changed my diffs over to RP max-gear, and didn't notice any mileage increase.
Complete changeovers(oil/diffs/trans/ps...) should be noticeable. One at a time usually isn't. Too gradual!
Go for it. Change the front/rear/x/trans/engine/ps with quality synths if you haven't already. If there isn't a MPG increase, add some air to the tires. That usually helps
Go for it. Change the front/rear/x/trans/engine/ps with quality synths if you haven't already. If there isn't a MPG increase, add some air to the tires. That usually helps
I wouldn't expect any.....I changed the tranny, transfer case and both banjos over to synthetic and noticed no change in mileage.
DEWFPO
DEWFPO
From what I've seen, this depends a lot on what type of driving you do. The biggest increases seem to go along with more highway driving. I had one customer say he gained 6 mpg in a full size Chevy after I changed his engine/ATF/rear end over to a quality synthetic. Don't expect that, but 1 or 2mpg would be a good possibility.
Sometimes this can be a tad bit tricky. I got almost 1 mpg and smoother running when I switch from a conventional ATF to Mobil One ATF. The Z06 Corvette comes stock with Mobil One 5w30 and the differential was already a synthetic, when I changed to Mobil One 75-90 GL5 product. So the only variable was the conventional vs synthetic ATF. So 1 mpg/24 mpg is app 4%.
[ November 04, 2003, 12:54 PM: Message edited by: ruking77 ]
[ November 04, 2003, 12:54 PM: Message edited by: ruking77 ]
Sure it depends on what kind of driving is being done.
Years ago, had a customer who reported a gain of several miles per gallon after changing front and rear differentials to AMSOIL. It was done in winter, in a car used mostly by his wife for short trip driving. The non-synthetic never got a chance to warm up, and remained just as thick as being taken out of a freezer.
Years ago, had a customer who reported a gain of several miles per gallon after changing front and rear differentials to AMSOIL. It was done in winter, in a car used mostly by his wife for short trip driving. The non-synthetic never got a chance to warm up, and remained just as thick as being taken out of a freezer.
Kestas
Staff member
I find it hard to believe some of the remarkable claims made in this thread boasting mileage improvement just by changing the transmission and diff fluid over to synthetic. Auto manufacturers are going to great lengths to improve mpg by a tiny fraction. I doubt they would ignore something as simple as switching their fluid specification over to synthetic to achieve the same results.
The only reasonable posts I read are Wayne's and DEWFPO. The others fly against the face of reason.
The only reasonable posts I read are Wayne's and DEWFPO. The others fly against the face of reason.
Kestas
Chevy spec'd GL-5 PAO synthetic in the rear end of my 2001 Chevy Silverado, I'll bet CAFE has something to do with it,
another note I just got 2MPG switching my diffs and transfer (3 differentials) on a Toyota FZJ80 (full time 4WD) to Chevron Delo witch is a good Dino gear lube, I don't think it was all due to the quality of new fluid but also the poor condition of the old fluid especially the front diff that was contaminated with grease from the front knuckles (bad inner axle shaft seals)
Chevy spec'd GL-5 PAO synthetic in the rear end of my 2001 Chevy Silverado, I'll bet CAFE has something to do with it,
another note I just got 2MPG switching my diffs and transfer (3 differentials) on a Toyota FZJ80 (full time 4WD) to Chevron Delo witch is a good Dino gear lube, I don't think it was all due to the quality of new fluid but also the poor condition of the old fluid especially the front diff that was contaminated with grease from the front knuckles (bad inner axle shaft seals)
Kestas
Staff member
You're right. Since I wrote that post, I found out that manufacturers are now paying attention to the CAFE gains afforded by switching over to synthetic diff fluid for factory fills. I still think the CAFE gains are tiny, but enough to justify the premium paid for synthetic diff fluid over the life of the fluid.
Some manufacturers have switched to synthetic for transmission fluid, but considering the premium to pay for 12 qts of (semi-) synthetic (as opposed to 2 qts for the diff fluid), I believe there's more at stake, such as longer life for the transmission, as well as adverse operating conditions, e.g., cold weather, towing.
Some manufacturers have switched to synthetic for transmission fluid, but considering the premium to pay for 12 qts of (semi-) synthetic (as opposed to 2 qts for the diff fluid), I believe there's more at stake, such as longer life for the transmission, as well as adverse operating conditions, e.g., cold weather, towing.
I had a 97 Land Rover Discovery that got 16.5 mpg with Mobil 1 5w30 before I attempted to increase the mpg with fluids/plug wires/plugs/air filter. The mileage went to 18.3 with Amsoil 75w90 front/center/rear diffs and Amsoil ATF. K&N and Jacobs wires took it to 18.8mpg. I switched over to Beru Silverstone silver core nonresistor plugs and picked up quite a bit of power but didn't get to do the highway mileage test as I left the area and never really did any normal highway driving except for the trip across country from N. Virginia to Phoenix in 3 days. Too high speed (75-95mph) to get a very good reading. I was getting 16.5mpg average for the trip. The last fillup in Flagstaff got me 22mpg for the 150 mile leg to Phoenix at 65mph and under (3am through the twisty mountains after 13 hours on the road). This vehicle has permanent four wheel drive and probably benefitted much more than most would. Never took it for another highway trip before returning it at lease end.
I changed out the diff fluids on my 2000 diesel excursion 4x4 and picked up about 11% highway and 8% local mpg. This was going from a 75w140 synthetic to a 75w90 synthetic.
I changed out the diff fluids on my 2000 diesel excursion 4x4 and picked up about 11% highway and 8% local mpg. This was going from a 75w140 synthetic to a 75w90 synthetic.
agreed, it offsets some of the cost of switching to synthetic, to figure if it will or how long it would take too pay for itself would require exact testing under controlled conditions and compared to new dino fluid not your old wore out stuff, not possible for us laymen
wulimaster yep full tiem $wd vehicles show fluid loss more than others, they have 3 diffs slinging 90wt arround instead of 1
Originally Posted By: sprintman
Redline say 6% achievable and I know there are documented trucks here seeing definite improvements. My Outback improved over the OEM stuff.
I switched mine to Amsoil synthetic ATF and SVG and did not expect nor notice a change.
If someone gets 6%, I think the old stuff might have been the wrong grade or maybe it was driveway sealer. Or they were smoking something.
Redline say 6% achievable and I know there are documented trucks here seeing definite improvements. My Outback improved over the OEM stuff.
I switched mine to Amsoil synthetic ATF and SVG and did not expect nor notice a change.
If someone gets 6%, I think the old stuff might have been the wrong grade or maybe it was driveway sealer. Or they were smoking something.
If you switch from something like 140w dino to 90w synthetic you will notice, 90w dino to 90w synthetic probably not.
I fully agree with full synth use in trannys and rear ends.
I thought some people on here were saying that synthetic gear oil isn't the greatest if you tow a lot? Is that true?
Originally Posted By: Miller88
I thought some people on here were saying that synthetic gear oil isn't the greatest if you tow a lot? Is that true?
I've never heard of that. The only thing negative about synthetic would be if you go from a thicker 140W to 90W because you are using synthetic, or if you extended your change interval, synthetic may not be great enough to justify the extra load on towing.
I thought some people on here were saying that synthetic gear oil isn't the greatest if you tow a lot? Is that true?
I've never heard of that. The only thing negative about synthetic would be if you go from a thicker 140W to 90W because you are using synthetic, or if you extended your change interval, synthetic may not be great enough to justify the extra load on towing.
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