In my experience the Amsoil stabilizer is far better than Sta-Bil. By mixing Amsoil's a bit stronger than called for, I managed to keep a one-gallon container of 40:1 gasoline-oil premix for my chainsaw and other equipment fresh for THREE years, and this was gasoline with 10% ethanol in it! What was left in the container, about a quart, finally went stale over the winter before year four. Both ethanol and oil are supposed to cause today's volatile fuel to go stale even quicker than it already does, so these results impressed me.