If the gas is just old (not turned to varnish), you can mix old gas with fresh gas in roughly a 1 to 10 ratio and use the gas for lawnmowers, weed whackers, chainsaws, and other gas powered tools. The greater portion of the new gas reinvigorates the old gas. You can do the same thing with a car, but it isn't recommended. The older gas still affects plugs and gaskets negatively, even in small portions.
By Suntydt from Tazewell, TN