V4.7 - Small Gas Engines hate Ethanol

This week’s column came to life back in 2009. I had been dealing with some lawnmower repairs and came to be friends with the gang at Riley’s Small Engine repair. While in his shop I kept seeing warnings against using gas/Ethanol in small gas engines. So, one day I asked what was his reasoning? He said it ‘builds too much heat in the engines and burns then up’.

Now, I’ve had some experience in running Methanol in my race car engines and they are both based on alcohol. But the one thing that alcohol does is make an engine run cooler- not hotter. At times, after a race, the intake would be iced over because of the coldness. So I asked myself “Self- how can something that makes an engine run cooler be ‘burning them up” ESPECIALLY when people run a gas/Ethanol blend in their car engines without any problems?

So, after much thought- here we go. First off, contrary to my first thought- cars DO have problems using blended (the technical name for a gasoline/Ethanol mix) fuel. Think not? Here’s a test. Find some straight gasoline and run it for two tankfulls and track the mileage. Then run some blended fuel for two tankfulls and track the mileage. You will not get the same mileage. The blended fuel gets worse mileage… and that is at the heart of the matter. Ethanol only delivers 62% of the equivalent Gasoline energy - therefore more ethanol (more as in quantity, not a higher percentage of the blend); must be used to deliver the same amount of energy.

In other words, when Gasoline delivers 100% energy, Ethanol can only deliver 62% of that, so more ethanol must be added to the engine.

In Automobiles, electronic fuel injection systems can make on-the-fly adjustments to the air/fuel ratio because of a closed loop in the computer that constantly takes a measure of the oxygen levels in the exhaust gas and if there is oxygen then knows the system is running lean and increases the fuel amount injected. Small gas engines have no such system, therefore, the engine runs ‘lean’ all the time.

THAT is the root cause of the small engines running too hot. Believe it or not, fuel also cools your engine, but if the air/fuel ratio is too heavy on the air part, the engine will run ‘lean’ and get waaay hotter than it should.

So, the bottom line is that you need to run straight gas in your weedeaters, lawnmowers, yard tractors or leaf blowers. Gasahol is somewhat OK for cars, but your small engines don’t have the electronic systems that are a must if your gas engine is to survive it. HINT, if you have an old car without the latest computers – don’t use blended fuel in it either.

Send your questions or comments to:
Toolsmartz@bellsouth.net and we’ll see what we can do to help you