Not recommending this procedure to others, but:
I have approximately 4 acres to mow. Start the lawn & garden John Deere on good gasoline, and get it up to temperature. Now add the older fuel. It will burn if the engine is hot, just doesn't start well. With 4 acres, I burn it all out, and then add some good fuel before shutdown. Only once had to let it run with no load for a couple of minutes when it was unhappy.
Jon.
