Comparison of 93 and race gases on oil dilution/damage.

[Toni]

Thought about this today when I was thinking at my desk. I currently use methanol injection and was curious on it's affects on the oil. When tuning using a lamda sensor most just leave the gauge configured for gasoline because it's familiar.

So the question is. What affects on the oil does 93 pump @ 10 AFR compared to race gas @ 10 AFR? The actual AFR # is just an example merely showing both have the same AFR when the gauge is configured the same. Race gas here can mean a higher octane fuel, like 100+, ethanol, 93+methanol etc.

I guess this boils down to volume of fuel leaching into the oil and it's ability to dissolve or otherwise alter the oils properties.

Thoughts?

[CoopKill]

Interesting thought. You slow at work? JK!

Good question I would like to be enlightened as well.

[Toni]

I shot the question off to blackstone labs. Curious if they have any input since they deal with oil ADL.

[CoopKill]

I wonder since E85/Methanol has been shown to degrade certain rubbers if it may contribute premature wear on the vss. Then again the oem fuel lines are claimed to be unharmed by it.

[sergechronos]

I wonder since E85/Methanol has been shown to degrade certain rubbers if it may contribute premature wear on the vss. Then again the oem fuel lines are claimed to be unharmed by it.

Perhaps it contributes, but cars since MTBE was phased in to replace lead in fuel. MTBE also causes deterioration of rubber parts similar to the effects of ethanol. Given that MTBE usage was increased following the Clean Air Act of 92, and the part numbers for VSS and such don't differ for later years, I find it hard to believe that it makes that big of a difference in the life on components. Although of course unless the factory VSS are viton based (don't think they are) we can't definitely rule it out as possible factor in their wear speed.

[Toni]

Reply from blackstone

Antoni,

The only fuel that might make a big difference as far as the oil goes is E85 due to it's methanol content. Methanol is more susceptible to water contamination. Still, if the engine is run frequently and doesn't have time to sit, the chances of finding enough water to cause any problems is minimal.

Any fuel will degrade the oil if fuel is found in high enough quantities. We don't see any difference in our data of one fuel causing more problems than the other. Most engines should have less than 2.0% fuel in the samples we test, otherwise, it could show a fuel system problem. That would be more of an issue, rather than the type of fuel in use.

We do see performance engines that run E85 with a lean mixture tend to wear more than others. Running any engine lean will cause cylinder head temperatures to increase, causing more wear.

I'm not certain on whether running the same air/fuel ratio is okay with the different fuels, but none should be in the oil in the first place. If fuel is present in high quantities (2.0%+), that could show fuel system problems.

You should contact a tuning shop for further details of running the same air/fuel ratio. They may be able to give you more information.

Thanks for contacting Blackstone!

Samir Kharbas
Blackstone Laboratories

[mjannusch]

Methanol content in E85? What? Hope he meant Ethanol.

Ethanol does absorb more moisture out of the air than gasoline, and if you let it sit long enough it can have negative consequences.

You can't run the same Air/Fuel ratio on the different fuels (gasoline vs ethanol vs methanol) as each has a different lambda. For instance, if you inject the same amount of fuel and get an effective ratio of 11.5:1 on gasoline, to get the same "11.5:1" effective ratio on E85 you need to inject 7.4:1 fuel, or on methanol you need to inject 5:1. What you are really doing when running "11.5:1" on a wideband display calibrated for gasoline is running the same Lambda which ends up being the same ratio of combustible elements in the fuel to the available oxygen in the air. The fuel's composition determines what ratio results in the correct lambda.

You really shouldn't have significantly more fuel in your oil with E85 vs gasoline, unless your piston rings aren't sealing right - in which case you've got some other problems to deal with. Hot oil should evaporate the ethanol anyways, so whenever you heat the car up it should bake out the ethanol.

Don't run overly rich, and don't run long on the oil changes if you are concerned about it.

[CoopKill]

Hmmm, I did not think about the hot oil baking the meth/eth out. Good point!

[TurboSinceBirth]

I believe too rich on any fuel will dilute the oil. I noticed with both 91 pump and E85 that 10s was too rich to run. My oil smelled like fuel on my motor but it's also stock with a lot of miles. I typically will run low to mid 11s on pump WOT with less boost and a hair more timing since that makes more power than with more boost. With the ethanol I found low 12s AFR WOT to make the most significant seat of the pants torque increase. It also ran crisper and I didn't have misfire issues either. So far the oil has not been diluted with fuel either. This is all on the gasoline scale too fyi.