When Good Gasoline Goes Bad

I had never heard of “bad gasoline” until I moved back to the country – in my case, to the Blue Ridge Mountains of Virginia. Even growing up in the corn fields of Iowa, I had not encountered this notion.

When I heard it from my country brethren, I snickered quietly under my breath. Even when I could not start my lawn mower, and the local mechanic somberly pronounced that it had “bad gas” in the tank, I rolled my eyes silently. Country boys fooling with a city slicker, right?


Bad gasoline is a major problem for engines, both in automobiles and in seasonal vehicles like motorcycles and lawn mowers. The issue is primarily the complex blend of chemicals used to give you better gasoline mileage. To do this, they have to make the gasoline very volatile – able to burn crisply and cleanly in the engine. But if the gasoline sits, those chemicals dissipate, and what is left is a sludgy petroleum product that can clog the carburetor and cause the engine to run badly, if at all, when it is next used.

But that is not all of the bad news. Turns out that another major problem is water condensation. When gasoline sits – and especially if the gasoline is cut with ethanol, which nearly all gasoline is today thanks to the irrational policies of our federal government – it is prone to draw in water. Ethanol attracts water from the air, which is why it is worse for an engine that is only run occasionally than pure gasoline. This, by the way, is the basis of claims that “ethanol is bad for your engine.” It probably is not if the engine is used constantly, though it does reduce your mileage while it reduces hydrocarbon emissions.

Back in the days when we oxidized gasoline to reduce bad emissions, oxidation of the engine was also a problem. That is less common today, since farmers have discovered they can get rich by promoting ethanol as a fuel rather than a food. (Point of order: Henry Ford initially built his Model T to run on ethanol, before the petroleum industry concocted gasoline. We might have been far better off had we stuck with ethanol as fuel. That’s an argument for another day, and another post.)

So what should you do? Four things:

  • Empty the tanks of seasons engines if you can – lawn mowers, gas trimmers, motorcycles, etc. This will get the gas out of the tank so it does not go bad.
  • If you don’t empty the tank, as most of us south of the Mason-Dixon line do not, either fill the tank to the top for the winter (a full tank does not have problems with condensation or evaporation) or make sure you put some fresh, new gas in the engine before you run it. New gas will take care of most of the potential problems.
  • Run the engines during the winter. This is fun if you have a motorcycle, but a pain in the butt for lawn trimmers and lawn mowers.
  • Buy your gasoline at stations with a lot of traffic. Many of the problems that are encountered come from gas that has taken a long time to get from the refinery to your tank. If you buy from a place that does not sell much gasoline, you are just asking for old gas.

The longer I live here in the country, the more I learn to respect the folk lore related to life, liberty and love. The characterization of country folks as “clinging desperately to their Bibles and their guns’ may make for great humor and derision for urban dwellers, but seems to make more sense as a way of life here in the country.


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