"The best advice on this thread was given by Cthoops. Dump your fuel into a car once a month and replace it."
A few months should be no problem. If it is wrong in your boat it is OK in the $30,000 car? Plain nonsense.
I think you're being a little tough on the guy. He's saying that if the gas is approaching its shelf life, burn it off in a vehicle that will consume it faster (and diluting it with the fresh fuel in the car's tank also helps). One month may be sooner than needed, but there's little question that one month old gasoline will be perfectly fine in a $30,000 car, as long as it doesn't have 2 stroke oil in it.
My understanding is that there are pretty much three stages:
- Gas absorbs moisture
- Gas/water mixture oxidizes and creates acid
- If gas absorbs so much moisture that it phase separates, the bottom water-rich phase is very concentrated in acid, and when sucked into your engine can cause great harm.
To address #1 and #3, seal the vent on your tank, if you can, and keep it full to minimize head space. And if you have a plastic portable tank and see the sides bulging in warm weather or sucked in during cool weather, do not open the vent to release the pressure or vacuum, because this will allow more moisture into the head space of the tank.
To address #2, use an anti-oxidant additive. Search around for reviews on which ones actually work.
One other thing that I do is to burn the gas out of the carb after every use. Some say that they'd rather leave gas in there to prevent condensation, but for me I've always burned it off and never had a problem with my auxiliary motor on my sailboat or my 50 hp outboard on the Trophy motorboat. I think this may be especially beneficial on older outboards (like my 22 year old 50 hp), since they were not designed for E10, and hoses and seals may deteriorate faster if exposed to the ethanol 24/7 than if they're just exposed while in use.
Ethanol gas is mandated in virtually all urban and suburban areas (which are subject to EPA emissions regulations), and some states have banned it in rural areas too. E10 is here to stay, so we might as well learn to deal with it.