Rick's Free Auto Repair Advice

Does premium gas last longer?

Does premium gas last longer than regular gas?

Debunking the theory that premium gas lasts longer than regular

Most regular octane gasoline contains ethanol. Ethanol gasoline has a horrible reputation for having a short shelf life. Most small engine manufacturers state that you should not leave ethanol fuels in your small engine for longer than 30-60 days. In fact, when using ethanol gas in a small engine, most engine manufacturers highly recommend treating fresh ethanol gas with a fuel stabilizer when filling the gas can at the pump

Fuel stabilizer does several things:
• Slows down oxidation from exposure to air
• Contains a metal deactivator to slow down corrosion of metal parts
• Slows down or prevents “phase separation” of the ethanol from the gasoline

Ethanol is a water loving chemical. It quickly absorbs any moisture in the air or gas tank. Most small engine gas tank caps are vented to the atmosphere to prevent fuel tank collapse as  you use the fuel. So ambient air is always moving into the tank. As ethanol absorbs more moisture, it reaches a point where it separates from the gasoline and falls to the bottom of the tank. At that point, the small engine carburetor is sucking in water laden ethanol instead of gasoline.

Premium gasoline may or may not be made with ethanol

Many people believe that by its very nature, premium gasoline doesn’t contain any ethanol. That’s false. Ethanol can be used to increase the octane level of fuel. Some gas stations do sell premium fuel with ethanol. If the premium fuel you buy contains ethanol, then it has the same short shelf life as regular octane gasoline with ethanol.

However, ethanol free premium gasoline lasts longer than regular gasoline with ethanol. But the same can be said of ethanol free regular gas, as compared to regular octane gasoline with ethanol.

So the question of whether premium gas lasts longer than regular gas comes down to whether the premium gas contains ethanol or not. If it does, then premium gas doesn’t last longer than regular gas with ethanol

If it’s ethanol free, then premium gas lasts longer than regular gas with ethanol.

©, 2022 Rick Muscoplat

Posted on by Rick Muscoplat

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