With the way gas lasts now is crazy. But I have found a way that last . I work for a race car shop full time, but my part time job is getting cars up and running for the Collings Foundation where they have a wide collection of cars planes and tanks. Over the years I have gotten a lot of cars up and running for them . One in fact was a car owned by Al Capone. Last time it ran was 1978. In 2011 I was asked if I could get it running, after Rebuilding the frozen water pumps and starter and a few tricks. I got it running. Well we use the car for about an hour 2 times a year. All of the cars that I get running I have been using avgas it has a 7 year life span. I have tried all different additives and nothing lasts. I also put in a like mystery oil to loosen things up.