Stability makes an additive specifically for ethanol treated gas, e10 is a great way to extend an oil supply, at 10%, over a period of ten days, we've done the equivalent of going an entire day without using petrol, and America consumes roughly 81 million barrels every day(plastics, fuel, packaging, makeup, and all that stuff that comes from crude), saving a day's worth every ten is pretty darn good, and it adds up. IMO that if you think you need an additive for any fluid, then you need to buy better quality, though with fuel, the reason it degrades is microbials in gas and diesel consume the good parts and leave the [censored] behind for us to dump into our motor. Sta-bil additive inhibits (slightly) those microbes from eating, allowing it to sit longer. From my own experience, the best way to avoid bad fuel, or going bad, is to avoid buying any more than you need, gas isn't cheaper bulk, so your not saving money buying more to store away. It's actually possible for ethanol treated gas to be able to sit longer, the ethanol itself gives the microbes a great deal of trouble just surviving in the fuel, and the higher the percent the longer it can sit without going bad(assuming you've properly sealed the container to prevent moisturizing.)
-srv