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What Fuel is Best for Small Engines

Today, the majority of the fuel that you buy at any gas station or convenience store is going to contain around 10% of Ethanol (often referred to as E10 gas).

The government’s Renewable Fuel Standard Program has required that Ethanol be blended with gasoline as a “Greener Alternative” to more harmful oxygenators such as lead or MTBE (methyl-tertiary-butyl-ether).

Problem with high alcohol content gasoline

The biggest problem with using the grain or sugarcane based fuel additive is that it is an alcohol. As the alcohol naturally separates from the petroleum-based gasoline, it has an affinity for attracting water.

This instability is called “phase separation” and has reduced the shelf life of the gasoline that remains in your small engine’s tank or that which is stored in your gasoline can.

Most experts agree that under ideal conditions the shelf life of E10 gas is only about 3 months.

If you live in hotter, more humid climates, it is much less. Once the fuel is contaminated, the bad gas can cause filters and carburetors to become clogged as unprotected rubber hoses and plastic parts actually begin to dissolve.

Although some fuel stabilizers can help, there really isn’t a miracle product available for today’s cheaper small engines.

Gasoline for Small Engines

For most small engines like leaf blowers, snow blowers, generators and lawn mowers, an unleaded 87-octane gas is fine with most US gas stations will adjust the gasoline mix with 10% ethanol or 15% MTBE (methyl tertiary butyl ether).

You will want to avoid E15 (15% alcohol) or E85 (a.k.a. flex fuel; 51 percent to 85 percent alcohol – want to learn more about E85? Click Card and Driver article here) which will reduce the lubricant efficacy and cause early engine wear and tear.

If you have a difficult time starting your small engine (especially if you left some old gas in the tank), you will want to use a canned fuel product which is ethanol-free (i.e. True Fuel for 2 cycle or 4 cycle engines).

Since most gasoline mix begins to deteriorate in as little as 30 days, you will want to use a fuel stabilizer like Sta-Bil to keep it “fresh”.

Mixing Oil and Fuel for Small Engines

For 2 stroke engines, always mix a high-quality 2-cycle oil like Echo Power Blend.

4-stroke cycle engines do not need oil mixed in with gasoline.

Small Engine Fuel Storage

In addition to Sta-Bil (or something similar), it is imperative to store fuel in a cool, dry location to prevent fuel degradation which may cause gumming or varnishing.


In time, we will likely find an alternative to Ethanol as a gasoline oxygenator, or even better, an alternative to petroleum-based fuels.

But, until that happens, you should try to limit the length of time that E10 is kept in either your small engine’s gas tank or fill can.

If your motor requires the choke to be engaged (even slightly), it is likely time to thoroughly clean the fuel lines, filters and carburetor.

After that, try to limit the amount of time that you leave E10 in tanks or cans.

Whenever possible, run the tank dry before storing your lawn equipment, mower, scooter, go kart or other powersports equipment.

Many of these small engines also have a drain plug at the bottom of the carburetor bowl for that very purpose.