Mechanics Corner: Small Engines vs. Ethanol

Automotive advice from The Under the Hood radio show

We love all things mechanical on Under The Hood. Simply put, if it burns fuel, we love it. A couple of us on the show are old die-hard powersports fans too, having owned dozens of motorcycles, three- and four-wheel ATVs, boats, and many Jet Skis. Add to that all the lawnmowers, blowers, and trimmers piled high in our garages over the years – you could say we have more than a little experience with small engines. 

When you own a small engine, you know that it is nothing like a car in terms of maintenance. Every year you seem to have a dead battery, and if you let one sit over the season without use, you can almost be assured that next year the fuel will be so bad that it will have to be changed. Sometimes the fuel has become so bad that a carburetor must be rebuilt or even thrown away and replaced. We know many people in the business of small engines and we have great respect for them. But until I talked to one of them about our own experiment, they were convinced that the reason for the failure of fuel systems was linked to ethanol — although they could not cite why. It was simply an opinion.

I have several Wetbikes along with a couple Jet Skis and an old lawnmower. Life got busy so all these toys have not left the shed for three years. You can imagine what happened. They all have battery maintainers so they are still in good shape, but the fuel in the tanks is so sour that it had to be changed in all of them and one will need a carburetor. They all have E10 fuel in them except for the lawnmower, which has a 5HP engine. These engines range in years from 1978 to 2003, and the only change to the fuel containment systems made within the past ten years has been fuel lines. Old lines should be kept up-to-date no matter what fuel you use. 

Replacement of the one carburetor — which happened to be the only one without ethanol in it — was due to the fuel evaporating and leaving behind varnish and sediment in the jets. The important part to note was that there was no damage of any kind seen due to the ethanol. The floats and bodies of the carbs looked good. 

If ethanol was harmful to small engines designed to run on it, we would expect to see some damage on these older ones that were not designed for it — but that was not the case. Even the lawnmower, which was run on 100% traditional gasoline, was in worse shape than those run on E10. Some even get better with age. If the alcohol is mixed with something else, it is subject to the expiration date of that product. 

We would have to say that what we have seen in these small engines is a good experiment, but you can research it yourself. Look up what happens and what is left behind when straight gasoline and straight ethanol evaporate. Keep the small engine maintained, use a fuel stabilizer, always follow the manufacturers fueling requirement, and do not let them sit and they will most certainly be in much better shape. 

We have a local go kart track that has been using ethanol to power its small engines for years and the results there have been similar. 

People are not afraid to use ethanol in their small engines when the manufacturer “allows” it, and the results  speak volumes. It’s time for everyone to reevaluate the way they view ethanol in fuel, for both small engines and cars.
We are not afraid to use ethanol in our small engines when the manufacturer allows it and we follow the content they establish. 

Take care, The Motor Medics. 

The Under The Hood radio show is America’s Favorite Car-talk show heard on over 230 stations and podcast. The Motor Medics, Russ Chris and Shannon are three great friends having fun and offering a wide range of automotive advice without the aid of in-studio computers or reference guides.




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