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Old 10-03-2011, 04:46 PM   #1 (permalink)
MetroMPG
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Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
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Blackfly - '98 Geo Metro
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Last 3: 70.09 mpg (US)

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When is "old gas" too old to use?

An article on Autospeed got me wondering about this.

I was surprised to read the experts giving answers that were much shorter than I would have expected.

Depending on whom you ask, gasoline is good for ...
  • 6 months - in a sealed container, after which it starts to degrade
  • up to 12 months in a sealed container
  • "several months" old fuel in your tank risks fuel system problems
  • "several weeks" is enough to detect octane degradation, based on dyno testing
Read more from: The Life of Fuel - How long does fuel last in your car's tank?

When I got the Firefly, it had been sitting, the tank nearly full, for seven years. The engine started normally on the old gasoline, and it ran apparently fine when I test-drove it around the block.


7 year old gas

7 years seemed pretty extreme, though, and I was warned that old gas could gum up the intake valves and make them stick. So I drained the fuel tank to nearly empty, drove straight to a gas station and filled up with fresh gas before driving it home.

OK, so if 7 years is too much, how about four years? That's how old the gas is in this 1990 Swift GTi:


4 year old gas

... and with a boost, it started right up after sitting in a field for that long.

On the other hand, I have had trouble running a 2-stroke boat motor with fuel that was 2 years old. Maybe it depends on the engine, or the oil mix causes things to go wonky sooner.

Autospeed: The Life of Fuel - How long does fuel last in your car's tank?

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