Hi John, never muck around with old fuel, it has a very short shelf life. You can buy fuel stabilizer but I would not use it after 6 months. 3 months and the bonds in the fuel molecule break down and you get more "knock" in your engine. The old lead fuel used to stop the knock but is a health problem. Oil breaks down as well. Even if you are not using the engine. There are all sorts of additives in fuel and oil these days that react to cause breakdown. The extra cost can help to preserve your engine and give you better start up response; increased performance; and fuel economy. Let your engine warm up for a while, but not for too long, when you increase the revs you get higher oil pressure on a 4 stroke and hence better oil pressure to lubricate pistons and bearings. Cheers.
