Any testing on mpg effects of using various gear oils?
 

* regular dino gear oil

* full synthetic (same viscosity)

* synth ATF with added Lubegard or Militec or moly additive

i saw a 3mpg increase at 72mph on my first tank. (over 11% increase)..
with the blizzard, i can reliably get another reading this week.
maybe next week or so.
full synthetic engine oil and full syth trans fluid, same velocity for my accord

You can start here. Some good stuff in there.

In theory, you shouldn't see a gain from using synth over conventional in the same viscosity.

i should double check the oil that was put in my engine.. the oil change place looked-up my car to choose the syth oil

As far as I know...viscosity is more controlled with synth vs dino gear oil...meaning that when cold synth is thinner. One person claimed that after changing to synth gear oil...same weight...he could coast further with synth oil.

I had an '86 Escort that used ATF in a manual transaxle....thinking that using synth ATF with a good additive might work...but might be risky too.

Good link!

Ford recommends the use of Mercon-based fluid in almost all their manual transmissions, with few exceptions, that I'm aware of. You're correct thinking that synthetic, as a rule, is more stable. I'm not sure this applies in a transmission as much as in an engine, but I can't really support that thought.

Using synth ATF that applies to the same specs as your original trans fluid will be fine on it's own. You can go to Ford dealer and get a 4oz can of friction modifier, but it's probably not necessary for the older trans?

If you search bwilson4web's posts, you will also find documented testing showing the effect of changing gear oil type/viscosity in his gen. 1 Prius.

The viscosity stability of synthetic gear oils should return better efficiency in cold conditions. It's an issue for transmissions/differentials, since they don't benefit as much from the heat of combustion as engine oil does.

I can find dozens of links that claim to support this notion.... but can I find one on short notice that appears to have some science behind it? Nope!

Anyone?

That's what I'm getting at. I've never seen/heard of a real benefit that was measured in a scientific sense, or couldn't have been explained by old fluid vs new, so I can't suggest in good conscience that there is any discernible gains from using synth over dino for the most basic of comparisons. Longer change interval isn't really even going to come into play, since many vehicles operate their entire lives on whatever fluid was installed at the factory.

Two references to improved fuel economy with synth gear oils below.

The fact that they appear on major manufacturer web sites (which employ lawyers to ensure they avoid or can defend legal challenges of their claims) says something, in my opinion:

Mobil Delvac Synthetic Gear Oil 75W-90, 80W-140

Castrol USA - Gear Oil

Darin -

I'm not doubting that there could be something about those oils/lubes that could return better fuel economy, but looking at the sites you posted, they don't really appear to be "claims" when read in context, so much as suggestions. They're also not "en comparo" to anything else.

For example - on the Delvac site, there is a table which lists features in one column, and their "advantages and potential benefits". Potential, sure. Actual? We dunno.

Later on the site, they suggest that you use it in tandem with some other fluid/additive for max fuel economy/wear/life:
Clever.

The Castrol site says:
So it's not really a claim so much as saying that "we're really trying". Again, with nothing in comparison, which means the claim could be fulfilled just by changing your old fluid, which will obviously give you an FE boost simply because it's worn out.

Unfortunately, I'm not going to be able to test it, either, on my F150, because any gains I see could be attributed to having changed the fluid that's been in the truck since 11/95 when it came off the assembly lines.

So, in closing, while I don't doubt that there is something about some synthetic lubes that can improve fuel economy, I, in good conscience, can't say for sure, because I have yet to see a convincing piece of data which shows an improvement and couldn't be attributed to some other variable.

I was thinking perhaps a large truck site might shed some light since they are more likely to be aware of such things.

Maybe Greyhound or US Postal Service?

Even a small variation will mean big bucks with the distances those trucks cover.

Pete.

Pete: the one study I've seen which purported to scientifically demonstrate the MPG benefit of synth gear oils was done on large trucks. I just can't find it now and threw out those other two links instead after a quick search.

Christ: agreed. Those pages use weasel words talking about synth gear oils.

But by comparison, I don't think you will find the equivalent weasel words used by a major manufacturer about fuel economy benefits of synth vs. non-synth motor oil (of the same viscosity). Last time I checked, they simply don't make fuel economy claims for the motor oils. That says something to me.

Except if "they" are Mobil... who makes a claim based on changing oil viscosities (which should be obvious, because there is no 0W dino), and I've even heard reports that the only way you'll get the "gain" they claim is by changing your old oil to their new oil, especially if you have quick warm-ups as is, since the only viscosity change is the "cold" measurement, going from 5w or 10w to stable 0w.

Here's a manufacturer claiming a 1% fuel economy improvement for large vehicles by going with its synth gear oil vs. mineral (of a different weight - duh), or "other" synth oils:

source: Roadranger FE 75W-90

More grist for the mill:

Here's a manufacturer claiming a 1% fuel economy improvement for heavy duty trucks by going with its synth gear oil vs. mineral (of a different weight - duh), or "other" synth oils:

source: Roadranger FE 75W-90

I'm changing over to Mobil 1 synth 75w90 LS in transaxle/diff (4x4) along with 1 oz per qt Tufoil.

Going with Mobil 1...0W30 synth oil in the engine (+ 1 oz Tufoil / qt) along with a Pure One PL30001 "Mustang" oil filter on a 1.5L engine. Oil can be found at Walmart for $23/5 qts.

Can see why I never did this before...since the almost 6 quarts of gear oil needed can be had for around $20 in dino...and around $60 in synth...and this isn't Redline or Amsoil. But it's good for 30K...so an extra $12 a yr.

I use the filter on the right....the one on the left is typical for the 3AC engine....

http://www.nonags.org/members/nijqk/3filters.jpg


Intend to run the motor oil for 12K...with a filter change at 6 months. Hopefully no more than 3 extra top up and filter quarts will be needed over 1 yr.

Might change my user name to Slick. :thumbup:

THis may start a debate and is not directly related to the overall topic, but... After each off road race in my desert truck I would cut open the oil filter to inspect for engine damage, (copper, gold colored bearing material). I tried many filters, I was most dissapointed with Fram filters and highly impressed with Wix filters for the amount a surface area on the fliter element. I think Napa does have a rebranded wix filter. FWIW (for what its worth)

Here are few fuel economy related finnish test:

http://www.motiva.fi/files/1027/2006..._eng_final.pdf
oil test section begins from page 46

http://www.motiva.fi/files/950/annua...ng_07-rev1.pdf
begins from page 30-

http://www.motiva.fi/files/948/annua..._-2007_eng.pdf

Due to less relative wind resistance and less relative weight typically carried (relative to engine HP?)...I think personal vehicles are more sensitive to engine/driveline lube viscosities and lubricity? Maybe by a factor of 2 or 3? Just a guess....

Anecdotal stuff....

Preparing my Saturn SC2 for the "Switch"? - Bob Is The Oil Guy

Two days in, and I'm already noticing improved cold starts (don't have to hold down the key to get it to catch like I did with GTX on really cold days), and my gas mileage is up about 4.5 MPGs. 6 qts. Mobil 1 0W-30 K&N Oil Filter CHANGED FROM Castrol GTX High Mileage 5W-30

Tercel4WD.com • View topic - Slippery Slope

"So just before we took the Tercel on the 2,500 mile trek, I changed the tranaxel and rear differential over from 89-90 gear lube to Mobile 1 synthetic. First drained the units, cleaned the magnetic plug ends and flushed/cleaned with cheap ATF then drained and filled with the synthetic.
Now I had no way of comparing the improvements to mileage or much of anything for that matter until I did my coasting route down Academy Boulevard. Normally the stop light catches me a Wyoming so when I get green I accelerate to 35 mph and put him in neutral. I have a mile of downhill that only has 1 stop light that I usually cruise through. Now with the 80-90 gear lube, the Tercel would slowly gain speed and top out about 42-45 mph, just the speed limit. This would be the case in summer and in winter with the gear lube viscosity restriction, he would get to 38-39 on this stretch coasting.
Lo and behold, Now he zips right past 45 mph and I actually have to feather the brakes to stay under the speed limit. I know this is not very scientific. I don't care."