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erichw1504's avatar

How long is unleaded gasoline good for?

Asked by erichw1504 (26331 points ) September 2nd, 2009

I recently had a problem with my lawn mower. It is almost brand new (just a couple months old) and the motor wouldn’t stay running for longer than two seconds. Then I realized it was probably the gasoline I had in it, which was almost a year old. So, it ran perfectly fine after I replaced it with new gas.

This got me to wondering exactly how long is gasoline good for? Is it different for other type of gasoline? Does it vary on what type of machine it is running on?

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4 Answers

Harp's avatar

Gasoline oxidizes over time, which produces gums. These turn into a kind of varnish that builds up on engine parts during combustion, and will eventually impair efficiency. How quickly that oxidation happens depends on several factors. Some refiners add chemicals that retard oxidation, others may not. Storage at higher temperatures, or in containers that allow more air exposure will favor oxidation. There are additives called fuel stabilizers that you can buy from auto supply stores which are anti-oxidants; these will extend gas life to over a year.

You can often see the signs of oxidation. If you compare fresh gas to oxidized gas, the older gas will look darker and cloudier. This is caused by the gums that have formed. You can sometimes see clumps of the gums in very oxidized gas

CMaz's avatar

When poured into ice trays and frozen. They make for a cool snack on a hot summer day.

OreetCocker's avatar

Tends to start to turn after about 6 months in a petrol tank, you call tell though as the smell changes.

Bagardbilla's avatar

Mowers are notorious for leaky seals in caps. Often moisture builds up in their tanks rendering them unworkable. Changing out the gas helps… If you pour out the gas in a clear jar, you’ll often find water at the very bottom of the jar.

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