Does Gasoline Go Bad? Don’t Find Out the Hard Way!

While it may seem trivial to some, the question “Does gasoline go bad?” is actually a pretty important one. If you store your RV for long periods of time, for instance, the answer to this question may be critical.

In fact, if you use gasoline for anything – a car, a generator, a lawn mower or any small engine – or if you have a gas-powered motorhome, today’s topic is for you. 

And if you’ve got some gasoline sitting in a gas tank in your garage, you need to understand its shelf life before you pour it into a small engine or your car’s tank.

That’s why we’re dedicating today’s post to answering the question of how long gas lasts and why.

Does Gasoline Go Bad?

In a word… yes! Gasoline does, indeed, go bad.

But the more pertinent question is “WHEN does gasoline go bad?” In other words, how long does it take for gasoline to go bad?

This question is a bit more complicated to answer because there’s no set time it takes for gasoline to go bad. There are multiple events that can influence the amount of time it takes before gas goes bad.

Some of the factors that come into play include how you store the gasoline, whether you’ve used fuel stabilizers, the time of year, and the percent of ethanol contained in the gas. (More than 98% of gasoline in the United States is an ethanol blend, typically E10 which is 90% gasoline and 10% ethanol.)

But generally speaking, properly stored gas is good for about 3-6 months.

What Influences the Time It Takes for Gas to Go Bad?

It’s important to understand the conditions that can shorten or lengthen the time it takes for gas to go bad.

For example, gas in the tank of your RV or car can start to degrade in about a month. However, under optimal conditions using a fuel stabilizer like this one can potentially extend the shelf life of fresh gas for a year or even more.

The three greatest influences on the degrading of fresh fuel (gasoline) are:

Water

Earlier we mentioned the typical 90/10 ethanol blend found at 98% of gas stations in the United States.

Well, ethanol attracts water molecules which shortens the shelf life of gasoline. The more ethanol there is in your fuel, the faster that fuel will degrade and expire.

Evaporation

Gas is made of hydrocarbons, and some weigh less than others. In the heat of summer, lighter hydrocarbon molecules evaporate. That’s why summer fuel blends contain heavier hydrocarbons.

Likewise, winter fuel blends have lighter hydrocarbons so that in the cold temperatures your engine can run smoothly. This makes starting your car or RV easier and allows your entire fuel system to run more smoothly.

This is important because evaporation leads to oxidation. 

Speaking of which…

Oxidation

Oxygen is one of the main parts of combustion, but it leads to oxidation. Oxidation causes less effective and less efficient combustion over time.

Is It Okay to Use Old Gas?

Not if you want to keep your rig or vehicle in good shape.

Old gasoline can, at a minimum, decrease your car’s overall performance and result in lower fuel economy. But gas that’s a year or more old can cause more serious problems like engine knocking, sputtering, and clogged injectors.

Gasoline is a mixture of volatile compounds. As it degrades, it starts to solidify and become gummy. As that gummy substance moves into your engine it can clog filters, damage the fuel pump, gum up the lines, and damage a number of engine components.

In the end, it’s far less expensive to buy new gasoline than it is to deal with the consequences when you see that “check engine” light come on!

How Do I Know if Gasoline Has Gone Bad?

Expired gas tends to be darker in color than fresh gas (assuming you can see it in your tank). It also develops a sour smell (which may be easier to detect, just by opening the filler door/cap).

With that said, it’s always best and easiest to clearly label any stored gas with the date.

How Can I Prevent Gasoline From Going Bad? 

If you have an engine you don’t use frequently (a lawn mower is a good example), try to find a source of ethanol-free gas or at least a low-ethanol blend.

If you need to store gasoline in a container, be sure to use only a gasoline-approved container that is clean and airtight. Store the container at room temperature or in a cool area.

If you plan to store your RV or another vehicle for a period of time, consider using a fuel stabilizer. There are several on the market.

The product we mentioned earlier in the post (which we’ll link to again below) uses additives that are capable of preserving the gas in your engine or generator for up to 24 months. Frequently used in stored vehicles, generators, and boats, it prevents gumming, rust, corrosion, and varnish that can cause very expensive issues.

Use the product only with fresh fuel and keep your gas tank 95% full to avoid condensation build-up during storage.

Be sure to run your engine for about five minutes or so after adding this product (or any fuel stabilizer) to your tank so that it can treat the entire fuel system.

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