2 Cycle engine oil and E85 gasoline don't go together?

This isn't exactly automotive, but seemed the best place to put this.

I bought a weedwhacker for the son-in-law yesterday, and some oil for 2 cycle engines. When I got home, I noticed a statement on the oil saying NOT to use it with E85 gas.

Why is this? Will it damage the engine? Will it not mix properly? Any ideas?

According to the Briggs and Stratton website, their 2 cycle engines are not made to run on E85 gasoline (almost an oxymoron).

In fact, only flex-fuel engines can run E85. My 2003 Honda Accord will run on a 10% ethanol mixture, but nothing more.

So, I'd say that the reason is probably that 2 cycle engines either won't or don't yet run on E85 and/or alcohol and oil just don't mix.

faqs.custhelp.com...

reply to post by GradyPhilpott

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Thanks, Grady, and thanks for the link also.

So, don't use E85 in my case.

Sometimes you don't have a choice.

That said, my 5 year old, low-time weed whacker has run fine on the gas sold here in N/W Arizona.
The gas station pump does state that there is up to 10% methanol in the gasoline.

I've also found that the gasoline with methanol kills your autos gas mileage approx 10%.
Very much the same is true with Californias MTBE additive gasoline.


When I was drag racing with little brother we found that running straight alcohol was fairly corrosive to carbureted systems.
It attacked aluminum as well as some of the fiber washers that seal carburetors.

Not to mention that it took about twice as much (straight) alcohol to generate roughly the same amount of horsepower.

(The basic rule is 2.0-1 for racing and 1.7-1 for street use on straight alcohol.)

Advantages were, alcohols high octane rating allowed us to run a 15/1 compression ratio.
(As compared to a maximum of 11 or 12/1 compression ratio on racing gas and 10/1 compression ratio for premium gas at the pump.)

Dis-advantages were, alcohol made it hard to start the engine in cold weather.

We got to the point where we started the engine on racing gasoline and ran it until there was some heat in the heads and switched over to alcohol.
Interestingly, the 15/1 compression engine rattled and detonated (ping) on the best racing gas we could buy.

After the races, we had to purge the fuel system of alcohol by running straight racing gas.


So far, with the 10% methanol gasoline I've done nothing more than run the weed whacker tank dry between uses.
Said use being perhaps as many as 2-3 days in a row.

I did slip up last year and forgot to drain the tank, but had no problems starting up on the old gasoline.
It does run better on fresh gas.

Gas/oil mix is 50/1.


Is E85 a stronger mix of methanol to gas as compared to the 10% stuff we're using here?


And . . . what are you supposed to do if only E85 is available and you're not supposed to use it in your engine?

(Double post)

[edit on 7-6-2008 by Desert Dawg]

reply to post by Desert Dawg

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From Wiki:


en.wikipedia.org...

Notice the construction difference in a FFV, which fits right in with your observation about the aluminum getting attacked.

They don't say what to do if E85 is all that is available. I guess you're supposed to come here and see what ATS says about it.

Thanks for the info.

Thanks for the info on E85.

Shoulda looked it up my own self.

Just to dispel the "scariness" of E85 for one... it is Ethanol not methanol. Ethanol is completely fine to use in any car, it will not corrode metal in your fuel lines/fuel injectors. However... ethanol contains less energy (BTU's) in 1 gal than gasoline does per gallon. So you effectively have to "burn" more to keep the same air-fuel ratio. As far as the weed whacker goes you can use E85 in it.. however you would have to richen the mixture up otherwise it will run lean and get too hot. Any car can run on it if it's been tuned correctly. With fuel injection you normally need larger fuel injectors and possibly a higher volume fuel pump. You also need to tune the computer for the new fuel injectors and set Stoitch to approx 9.7:1 where gasoline is 14:1.

[edit on 9-6-2008 by bigshow]

reply to post by bigshow

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Thanks for the input. What the heck is Stoitch? Never heard of it.

Correct my spelling first... it is Stoich. Basically it is the optimum ratio of fuel to air for proper combustion of the fuel. So gasoline is 14.7 parts air to 1 part gasoline. Ethanol is 9.0 parts of air to 1 part of ethanol.

Yes, it will. But the main concern is aluminum fuel tanks. Synthetic rubber is also not immune to premature hardening promoting leakage. So-called flex fuel vehicles use either anodized aluminum or stainless steel in places where bare metal contacts fuel, as well as teflon-lined fuel lines. There is also the issue of ethanol absorbing water with anecdotal evidence that this results in pitting in iron cylinder walls, however with this issue I would be most concerned with accelerated degradation of steel exhaust pipes.

Besides all that, I reason the big problem with 2-cycle motors is they typically blend their oil with fuel. Excessive alcohol in the oil will cause a loss of viscosity resulting in premature wear. Some FFVs recommend E85 rated oils to combat this problem, but I am not aware of any such options for 2-cycle. [this would explain why the warning is printed on the oil]


[edit on 10-6-2008 by apc]

I belong to a camaro (LS1) forum board and there are SEVERAL people who have been using E-85 in their non-flex fuel vehicles for several years without one problem. FYI an LS1 V-8 is an all aluminum engine 346 CI. One guy has a write up on how to configure the ECM to run on it and he lives in sweden where E-85 is much cheaper than gasoline. He has ran it for 4 years and 60000+ miles without an ounce of trouble.

That's nice. I guess all those big auto manufacturers have wasted millions of dollars in research and development on their vehicles. If only their engineers had read the postings on that Camaro message board, all that time and money would not have been wasted.

Regardless, the issue at hand is 2-cycle motors. I'm fairly confident in my conclusion that the reason for incompatibility is oil dilution. But then again those idiot automotive engineers seem to agree, so who knows.

There's no reason for a smartass reply. And I realize that my reply wasn't entirely about 2 cycle engines... however since no one is willing to "test" it then I see no reason not to try it as I will be converting all my lawn equipment to Ethanol and I expect no problems out of it. It seems the general consensus I get is everyone is scared of it... however many people think E-85 is Methanol which is a totally different animal.

There is every reason.

To succeed in such a venture you'll likely need to replace the piston or shave the head to up the compression and rejet. Also find some sort of oil blend that is not easily alcohol soluble. Maybe a fully synthetic with whatever additive the FFVs use. Seems like an awful lot of work just to save $0.50 per gallon in a weed whacker. I'd only try it on a junk motor first because if the oil solves you might not know it until the piston seizes.