Originally Posted by Brian.

I've got about 27 years under my belt as a motorcycle mechanic, so I've worked right through the change in fuel. "Bad" gas can be a whole lot of things, but when talking about age it nearly always comes down to oxidization. Pure gas can go about a year before it starts having issues, same was true for the MTBE years (was fully phased out by about 2000). Ethanol fuel can go about 3~4 months, though if you're in a HOT climate, a month might be showing problems. On a similar vein, if the fuel is kept in a sealed container (the new gas cans that don't vent) that's as full as possible (as little headspace/air), it can go longer. The reason for the short time is that the H2O it absorbs is introducing more oxygen that causes the fuel to "varnish" and go bad. It's no longer just the surface touching air, but now it's the moisture being pulled out of the air and into the fluid too....



Octane ratings have NOTHING to do with time before gas degradation. Sorry, you can think that all you want but it's not going to make it true. In some, rare, cases the higher octane fuel have less ethanol (or did, I haven't seen any in a long time), but it's a safe assumption that the base fuel platform is the same for any given brand, and the Only difference is extra additives to rise the octane.



Get into additives like StaBil, and you can get most of a year out of ethanol fuel in most cases (extreme heat and a nearly empty tank would be the major exceptions). I'm sure most of the additives are the same, I've just been a StaBil user for decades and haven't had need to look elsewhere.





If you have small engines that see only occasional use and want to give them the best fighting chance, drain the carb float bowl after every use. No, running it till it stops is not good enough (it'll actually make things worse). Then, fully top off the fuel tank. I've made a lot of money over the years cleaning motorcycle carbs in the spring, the people who heed my advice never come back (well, for that service, it usually earns me a lot of Other work though). those who don't, I get to see year after year after year....