depending on what kind and how much fuel is in it. i wouldnt leave a 1/4 gallon sitting around to long, its also best to store fuel out of sun light in a cooler area. from my own experience I think the stuff looses its zaz after 1 to 1 1/2 yrs. thats just resealed. I just try to use it up, I dont like running old fuel. some people dont shake there fuel either, so thats also a factor.