fuel decomposes..... 4 months old is gonna be bad... gas in the old days lasted longer but with all the newer additives, fuel is only good for about 3 months tops(a tank of gas only lasts a person a week ussually anyways)... if you want to store a car and keep the fuel in it for when you drive it again, you can put fuel stabilizer in the tank which will give you a little longer time before it breaks down...

if you smell your gas right now, you'll notice it smells just a little different