Ethanol in gasoline

Most people have heard of E85.  But have you heard of E10?  Many people have not.  But those same people unknowingly buy it all the time.  Most regular gasoline now contains 10% ethanol (E10).  So what does this mean for you?

For cars:

If you have a car that is labeled as “Flex fuel”, or is fairly new, then you don’t have much to worry about.  But if you have an older car, it can mean worse gas mileage and deterioration of fuel system and engine components.

-Ethanol requires higher compression engines to burn at peak efficiency, so using it in engines designed for pure gas can cause the MPG to decrease.

-Ethanol negatively affects rubber and plastic parts in your fuel system.  This causes hoses, seals, and other parts to break down, leading to the failure of those parts.

-Ethanol separates from gasoline if stored for long periods of time.  This is called phase separation.  When this occurs, the ethanol settles on the bottom of the tank.  This can result in your engine getting a high concentration of ethanol.  For engines made to run on pure gasoline, this can cause serious damage.

-Ethanol attracts water into fuel.  This can cause poor engine performance, rusting of fuel system components, and frozen fuel lines.

For small engines:

Many of the same points I made for cars apply to small engines.  But the problem is often compounded when fuel is left in equipment for long periods of time.

-One thing that is usually only noticeable in small engines, is the increased engine operating temperature when ethanol fuel is used.  The reason it affects small engines more greatly is because they are usually air cooled as opposed to liquid cooled.  The ethanol burns hotter and causes the engine run hotter than it was designed to.  This can put more stress on components and decrease engine life.

-Ethanol eats away at fuel lines on power equipment with small engines.  You may find yourself needing to replace fuel lines as often as every 2 or 3 years.

-Ethanol attracts water into the fuel.  This causes the fuel to go bad and small engines to run poorly or not at all.

So what can I do?

The easiest thing to do is find gasoline that doesn’t contain ethanol.  It will be labeled as “100% gasoline”, “pure gasoline”, or “no ethanol”.  There is a website,, that can help you locate stations that sell ethanol free gas.

If you are in doubt of whether or not gasoline contains ethanol, you can test it using a small testing bottle such as this one:

If you can’t find pure gasoline locally, there are still some things you can do:

-Try not to put more fuel in your vehicle/small engine equipment than you will use within two weeks.  The longer ethanol fuel sits, the greater the chance for phase separation and water absorption.

-Drain the fuel from the carburetor and tank on small engine equipment when they will be stored for long periods of time.

-Use a fuel additive like Ethanol Shield to help prevent ethanol related damage to your vehicle or small engine.

-Consider using a bottled premixed gasoline for small engine equipment that isn’t used frequently.  These fuels contain no ethanol and have a long shelf life.  The time and money you save on preventing repairs will pay for the extra cost of the fuel.  Some examples of this type of fuel are TruFuel and VP Small Engine Fuels.  You can usually find these at your local hardware or auto parts store.


Hopefully this has helped you become more informed about the fuel you are using and saved you from trouble caused by ethanol in your fuel.


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