Does gas really go bad?

Dear Car Talk

Dear Car Talk | Dec 01, 2000

Dear Tom and Ray:

I have a 1986 Toyota Corolla that keeps on going! My question is about
gasoline. I have started to walk the 1 mile to work for health reasons and
because gas prices are so darned high. I fill up my tank, oh, about once a
month or so. My husband says I should be using gasoline stabilizer to keep
the gas fresh in the tank. Is this for real? Does gas really go bad? How
long does it take to go bad? Please let me know, because I don't want this
to be an excuse for me to stop walking to work. -- Carol

RAY: Well, my brother happens to be the world's foremost authority on bad
gas, Carol. Ask anyone who's ever been on a long car ride with him.

TOM: Gasoline DOES go bad, Carol. And there are two things that happen to
it. One is that the volatile portions of the gasoline evaporate over time.
And that makes your car harder to start, since the engine counts on being
able to vaporize the gasoline in order to ignite it.

RAY: The other thing that happens is that "gums" settle out of the
gasoline. And these syrupy byproducts can gum up your gas filter (if you're
lucky), or your fuel injector nozzles or carburetor passages (if you're
less lucky).

TOM: But the good news is that, according to Lew Gibbs of the Society of
Automotive Engineers, gas really isn't in danger of going "bad" for about a
year. Gas can even be fine for more than a year. But a year is the point at
which gas is considered questionable.

RAY: So if you're going to leave your car for a year or more, then you want
to add a gasoline stabilizer and fill up the tank all the way to minimize
the gasoline's contact with air -- which is what causes the gums to form.

TOM: But if you're filling up the tank once a month, or even once every
couple of months, there's absolutely nothing to worry about, Carol. Keep on
walking. Good for you.


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