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John Smith
10-02-2009, 06:35 PM
I believe I've approached this subject before, but not positive.

Anyhow, here goes.

I've got a three gallon tank. As I've used the motor very little, tank is still half full. Gas is now 4 years old.

Is it still good with additives for gum and water in it? Do the additives need to be replaced?

goodbasil
10-02-2009, 08:01 PM
Gasoline has a life of 90 days.

Dan McCosh
10-02-2009, 08:29 PM
I've had substantial problems with old gas in the boat tank. Just finished dealing with it again=-weird stuff in the tank, clogged filters, etc. It's been a very slow season, with not much motoring. I don't think gas lasts a season, at best.

Bob (oh, THAT Bob)
10-02-2009, 10:11 PM
If the tank is vented, the more volatile (lower vapor pressure, easier to evaporate) constituents evaporate off. These lighter elements help cold starting. Old gas used to leave varnish deposits in the carb. Gasoline these days is cleaner than it used to be, required because of fuel injection, but I still wouldn't count on it, not with the cost of motor service (injector replacment or carb rebuild). I have had complete success in storing fuel over a winter with Stabil fuel stabilizer. When I owned a sports car (with injection), the owners club recommended storing with a full tank of fuel to prevent condensation, but with stabilizer added; add the Stabil, top off the tank at the nearest station, drive home slow to circulate through the engine, store it. Once the fuel goes bad, stabilizer will not fix it, it is a preventive measure.

That old fuel probably has water in it by now because the alcohol in all car fuels (not marine fuel) absorbs it. I would not use that fuel in anything expensive. If you want to use it, I would at least decant it off: Cut the top off of a 2 liter bottle pop bottle, then wash and dry the two parts; you now have a clear, clean big cup, and a funnel. Put a paper coffee filter in the funnel end, and put it over a clean fuel tank. Pour the old gas into the clear cup, then slowly decant (pour) it into the funnel. Water and sediment will stay at the bottom of the cup (and you can see it), don't pour it all off, pour the very last remnants into a waste cup and discard. Repeat.