I fill my lawnmower with the cheapest available gas, which happens to have 10% ethanol. The lawnmower is from Montgomery Ward, which gives some idea of its age. I don't put any additives in the fuel. After I'm done mowing the lawn, I put the mower away, and it usually has half a tank of gas. In the late fall, it snows, and I don't mow the lawn any more. I don't do anything special with the mower, and it sits in the garage all winter with a half a tank of gas in it. The next spring, I top off the tank, push the primer a couple of times, and start it up. It starts on the first pull, and when I'm done, I repeat the whole process.