Gasoline Shelf Life

February 19, 2006 3:53 PM

What is the shelf life of the gasoline/oil mix that is used in 2 stroke engines? I use my chain saw 2-3 times a year and mixing fresh gas/oil mix every time is both wasteful and creates a disposal problem. How often should the gasoline in my emergency generator be changed?
posted by Raybun to home & garden (5 comments total)

You can use a fuel stabilizer to prevent things from gooing up in there.

The first couple years I had my 2 stroke jetski, though I had no real problems, it was a bit hard to get started after sitting all winter -- I didn't drain the gas or run it dry or anything. After finding finding out about this stuff, it always started up right away, even after almost two years (missed a season with injury.)
posted by SpookyFish at 4:53 PM on February 19, 2006

I think you will find a lot of useful info in this previous question: Can I horde gasoline?
posted by Chuckles at 6:26 PM on February 19, 2006

You don't have to dispose of the oil/gas mix; you can use it in your car without ill effect. (The small amount of oil mixed with a full tank of gas isn't going to bother your engine or create smelly fumes.)

For the chainsaw, if that's the only 2-stroke machine you use, I would mix a small batch of fresh whenever needed, then chuck it into the vehicle. I find that any gasoline purchased over 30 days ago increases the difficulty of starting any yard machine; fuel stabilizer helps, but isn't a magic keep-forever card. The smaller the engine, the bigger the problem this is.

For the generator, your manufacturer's recommendations would be best -- I know some people run theirs regularly just as maintenance, but I don't know that they have to burn off the entire supply of fuel. You don't want the thing to be gummed up at the time that you need it.
posted by dhartung at 7:40 PM on February 19, 2006

Gasoline is good for 6 months to a year. You may get away with a bit longer if you use fuel stabilizer but I wouldn't bank on it, although it will probably stop the gas from turning to wax in the carburettor or air filter.

Diesel lasts way longer.

I tend to run my generator etc to empty before winter.

Diesel engines, however, should never be run dry as they are a nightmare to re-pressurise. (Most people who own a diesel tractor have run it dry exactly once).
posted by unSane at 8:09 PM on February 19, 2006

I have used gas/oil mix several years after it was bought. No adverse effect on the saws as far as I know. This was gas of the type you buy pre-mixed for low toxicity of the exhausts.
posted by springload at 2:13 PM on February 20, 2006