I recommend running a small engine until it is completely out of fuel at the end of the season. If you have too much gas in the tank, at the very least turn off the fuel petcock and let the engine run until it stops — if it is gravity fed and carbureted. This exercise will drain the carburetor and keep it from getting gummed up by varnishes and other crud that mysteriously appear and clog the system during idle months. If the engine uses a fuel pump or is fuel injected, follow the manufacturer’s instructions for storage. If you leave fuel in the tank, stabilizers can help keep it in top condition until the next time you try to start it. I have never personally had gasoline go bad in any machine. I have never used a stabilizer either, but some of my buddies swear by them.