Old gas

[bkaab]

How bad is it to run a car on old gas? What will the car run like on old gas? I just got my 96 Grand Prix SE all back together and running. Only issue is its not idling very well at all, exhaust smells bad. The car was parked with over a half tank of gas last October I believe. It has like about half a tank now and Ive added about 1 gallon of new gas to it. The car is throwing P0300 misfire code. Im thinking its just the old gas making it run like crap. But Ive never delt with old gas before so I don't know.

 

Should I siphon all the gas out or continue to add new gas?

[RobertISaar]

it CAN cause it.

 

if you have lawn equipment or otherwise stuff that doesn't require good fuel, drain it and run it in that.

 

otherwise, i'd top the tank with premium and burn through it.

[Garrett Powered]

add octane booster, xylene, or toluene.

[19Cutlass94]

When I was working on my car I had gas in the tank, about 1/2 tank, that was over a yr old. Started up and ran fine. Although you could tell it didnt like it.

[paulo57509]

Old gas will cause all kinds of idle and driveability issues.

 

Remove the filler cap and take a whiff down the pipe. If it smells like turpentine, the gas is definitely bad.