E-85 gasoline and small engines

I had to buy a new gasoline cap for my push mower with a 4 horespower Briggs and Stratton Quantum engine. The gasoline cap is labeled E-85. This part is a genuine Briggs and Stratton replacement gasoline cap. Now I have no intention of putting E-85 gasoline in my 20 year old mower. I was wondering, though, if new small engines are set up to use E-85 fuel. Since the energy content of E-85 gasoline is less than that of regular gasoline, I would think that a small engine wouldn’t develop as much power. Since cars get reduced gas mileage on E-85 gasoline, wouldn’t lawnmowers get less grass mileage on that fuel?

In general, small motors can take a lot of abuse as they don’t have to conform to the same polution standards as car motors. I don’t feel you will notice the loss of power immediately but perhaps long term. In my experience, you should still take extra precautions like using marine grade stabilizer for ethanol, Tru-Fuel for long term storage, ethanol treatment enzymes, or water separators for marine application. Now a little rant!

Even if your motor never sees the water directly, ethanol retains moisture from the atmosphere and precautions should be taken to minimize carborator problems over time. I feel the added moisture retention will cause the most problems in running, not the ethanol itself. Depending upon the humidity, it may not take long for this to occur.

Problems also vary with the size of the motor. Smaller carbs on chain saws for example with the smaller orifice’s may be more suseptible then say the carb on your snow blower.
Outboard motors (and snow mobile motors)are particularly problematic due to long term storage and proximity to moisture and condensation. Anything having to do with the water costs lots of $$$$$$$ to maintain and repair it seems. I now only run the very expensive Tru-fuel alone in my chain saw and power two stroke equipment that has to sit for long term, and flush my lawnmower and generator with it for storage. Thank you Uncle Sam for “saving” all that fuel and making small engine ownership hell.

I was recently talking to a friend of mine who is a chemist, and she said that in order for E-85 to be worth buying, it would have to be lower than 2/3 the price of gasoline. There is a station in my town that sells E-85, and at the price they sell it, using it would be more expensive per mile than the regular E-10.

Read your owners manual for the engine and not the gas cap. If you don’t have one, you can read them on line. I have several B&S and no way do they want anything more than 10% ethanol. In fact after having several carb problems I now only use non-oxygenated gas with the B&S stabilizer in all of my small engines. I’m quite sure the carb parts will not stand up to 85% ethanol. That goes for outboard engines too that can be destroyed using more than 10%.

Bing–I know that my old lawn mower manual says to use fuel with no more than 10% ethanol. I was just curious about newer small engines. I was surprised to see E-85 on the replacement gasoline cap. I don’t intend to purchase a new mower until the one I have bites the dust.

Only Flex-Fuel vehicles can use E-85 safely…The replacement cap is a spare for a special E-85 only engine Briggs must make for some obscure market or it’s some sort of “universal” fit replacement part that may fit dozens of other applications…

The B-S web site specifically states using anything with more than 10% ethanol will void the warranty. Wondering why they had an “E85” cap?

Thanks to all that reponded. I looked at the gas cap more closely. It has an image of a gas pump with E-85 in a circle on the pump and a diagonal slash through the circle which surrounds the E-85. It means not to use E-85 in the engine. My mistake. Sorry about the confusion.

Maybe E85 is the part number? Some other kind of reference number?

I typed the above before reading ALL the posts. Doh!

“Maybe E85 is the part number”

You’re not confusing it with the famous “710 cap”, are you?


I think that the E-85 in a circle with a diagonal line through the circle means NO E-85. The circle is inside a gas pump symbol embossed on the top of the gas cap. Perhaps someone tried to run a small engine on E-85 while the engine was within the warranty period, so replacement gas caps were made with this symbol. My mower was made in 1991, long before E-85 gas was available.
I can’t fanthom why anyone would want to use E-85 in a small engine (or any other engine for that matter), but I suppose it has been tried.

As a frequent poster here, you know that EVERYTHING has been tried. I bet antifreeze has found its way into a lawmower, sometime, somewhere…

Yes, and as a frequent poster I should have examined the replacement gas cap more carefully before I made the original post. I didn’t have my facts straight on this one. I did see that in one issue this year in testing lawn mowers, Consumer Reports tested a mower that is fueled by propane, so I figured it was possible that there might be a flex fuel mower. The propane mower finished at the bottom of the heap.

Well there ya go, the lunacy of those silly icons and the slash across them. For multi cultures and multi languages. You’re supposed to understand the difference between a fog light icon and a head light icon? Can’t they just say no E-85? Or head lights on like they used to? I had to check the dang owners manual to see what one of the icons was. A door with a lock on it??

Wow, sorry. Feel better now.

I was hoping for a definitive answer to this question. I saw a recent episode of “American Chopper” the other day and Paul Jr was riding his new creation for the DeKalb corn seed company. He claimed that he used straight ethanol in the chopper and that it ran great with no problems. I have a feeling that engine problems will show up in the near future.

I’m sure Paul Jr (with buckets of money from DeKalb) got the right jetting and materials in the carb to run E100 (not that he could buy it on the street) or E85, but I bet that’s all it could use, not any mix like ‘FlexFuel’ vehicles have to do.

I hope so texases. In the episode, the bike was already completed and the ethanol idea seemed like an afterthought.


For somebody capable of fabricating a custom chopper, swapping out a couple of jets would constitute “child’s play.” Alternatively, just riding with the choke “on” would give a MC capable of running E-100 well enough to please the cameras…

Most lawn mowers will not take E-85 gasoline. See my family is borrowing the landlord’s mower because the one we have is broken down and our landlord left us a bottle of fuel stabilizer the mix in with the gasoline. Don’t know why? We don’t put E-85 in the mower because it specifically says in the owners manual not use E-85. But I’m wondering what the fuel stabilizer is for?

I guess the gas cap I purchased was made for people who don’t read the owner’s manual. However, at first glance, it looks like it says to use E-85. I had to look closely to see the diagonal line through the circle which surrounds the E-85.