i think hes actually wondering if the 5month old gas is ok to use. ive had gas sit in tanks for longer than that and it fires up. the key is the smell. the less it smells like gas, and the more it smells like shit the less of a chance there is ts good. if it hasnt varnished yet, you can drain it easily if youre that worried about it. but 5 mnths isnt a long time for gas to sit nowadays. now if you start pushing closer to 9 months or a year or more, then you could have problems. i guess the other way this could be approached is what kind of gas is it??? if its high octane or exotic race fuel, its probably trash. not to mention other various parts. i know some of the vp gas will seriously screw up carbs and other stuff if you leave it in there.