Mechanics Corner: What Makes Our Engines Ethanol Friendly?

“What makes our engines ethanol friendly?”

This is the one question we are asked more than any other on our radio show and in our shop when we talk about the use of ethanol. Every day we have to make choices about our vehicles, and we make those choices based on today’s cost and our future costs incurred by how we take care of them over the long-term. It’s a valid question, and one we want to address, especially given all the negative press that ethanol has received around small engine use, regardless of truth. Let’s start with some truth about small engines and ethanol use:


Question one: Can too much ethanol damage a small engine?

A. It is possible to damage any engine when it is misfueled. Just like your car engine, which requires a certain range of fuel, so does that small engine. All engines are engineered for a specific fuel or blend. Most small engines have fixed, non-electronic adjustable fuel systems so they can only run set amounts of fuel content. Just like your car, you want to run what the manufacturer designed it for.


Question two: Can I use ethanol in the correct amount in my small engine without damage?

A. Yes, check out the owner’s manuals on today’s small engines, and you will find they tell you how much ethanol is safe for the engine. Since ethanol is in almost every pump in America, they are being designed to run on it.


Question three: Ethanol makes my small engine run hotter, so it will burn itself out, right?

A. Ethanol does not make a small engine run hotter. Incorrect use of a fuel by using higher than recommended blends, which cause the engine to run very lean, makes an engine run hotter. Misfueling will cause a lean condition and a hotter engine.


Now that we’ve given a little insight into small engines and how they run hotter when using a higher blend of ethanol above what’s allowed by their manufacturer and why, let’s look at your car.

Modern cars — those built after 2001 and many before that — have electronic fuel injection and timing controls. Most small engines do not. Those electronic fuel controls take instant, real-time measurements of the oxygen content coming out of the engine’s exhaust and instantly correct the fuel mixture, allowing for the optimal fuel burn and efficiency. If that mixture ratio needs to be changed, the computer has a wide range of adjustment, and if it has reached its limit, the check-engine light will come on to alert you.

Ethanol runs cleaner and cooler than regular gasoline; it provides less heat energy than gasoline, so it takes a different fuel ratio. Today’s cars are ready to use ethanol without missing a beat. Check your manual for the allowable amounts.

So, there is the difference between a small engine and your 2001 and newer vehicle using electronically controlled fuel injection, but there is much more. Cars are being engineered for more performance every year, and performance requires good fuel with higher octane. Ethanol can provide that higher octane at a lower cost than regular fuel of a higher-octane content. Just look at the pump price.

So, what’s the advantage of that higher octane? When an engine is not running at its most efficient level due to an octane level that’s too low, it loses performance and that means less fuel mileage. This is just one more reason for ethanol fuel: performance at a lower cost.


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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