We have a 55 gal drum of waste gasoline. This is gasoline has been removed from mowers, chain saws, generators, pressure washers and other small engine. We have to replace the ethanol gas with non-ethanol gas so these small engines will store better when not in use. There was nothing wrong with the gas otherwise (except water absorption)
This gas can be filtered and mixed with good gas to run in older carbureted engines. Old farm tractors comes to mind. If someone wanted to run a mix of this gas with fresh gas and had it filtered it would burn just fine. Perhaps someone has already been doing this with old gas. I think a mix of 1 gallon to ten gallons of fresh fuel should work OK.