Any testing on mpg effects of using various gear oils?

[Christ]

Originally Posted by MetroMPG

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.

[MetroMPG]

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

[Christ]

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:

Originally Posted by delvac site

Use as a companion with Mobil Delvac Synthetic Transmission Fluid 50 in transmissions for maximum drive train life, efficiency and fuel economy improvement

Clever.

The Castrol site says:

Originally Posted by castrol site

Synthetic based to maximize oxidative stability and fuel economy

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.

[Peter7307]

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.

[MetroMPG]

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.

[Christ]

Originally Posted by MetroMPG

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.

[MetroMPG]

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:

Benefits of Roadranger® FE 75W-90 Synthetic Axle Lubricant:

Better Operating Performance – 1% measured fuel savings (validated through fleet testing with an independent testing facilityutilizing SAE J1321 methodology)

source: Roadranger FE 75W-90

[MetroMPG]

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:

Roadranger FE Axle Lubricant is an API GL-5 extreme pressure gear lubricant designed for improved fuel economy in heavy- and medium-duty applications, as compared to typical petroleum 80W-90 or synthetic 75W-90 gear lubricants.

Benefits of Roadranger® FE 75W-90 Synthetic Axle Lubricant:

Better Operating Performance – 1% measured fuel savings (validated through fleet testing with an independent testing facilityutilizing SAE J1321 methodology)

source: Roadranger FE 75W-90

[suspectnumber961]

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....




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.

[Bajascoob]

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)