Recently I bought an old car (1954 Ford Zephyr, a six-cylinder 2.2 liter English car) whose recent history was essentially unknown to the seller but had probably done little running for some time. He warned me that the engine was not running correctly - the car was blowing black smoke and misfiring under more than a moderately open throttle. I checked the ignition system and timing, and dismantled the carb, checked its parts and reassembled with new economy diaphram and gaskets. That car no longer blew black smoke but the misfiring at anything more than 30% throttle, accompanied with spitting back through the carb, was still there unchanged. I was running out of things to check, when it occurred to me that the fuel in the tank might well have been there for some years. I drained the tank, put fresh 98 octane lead-free fuel in it and .... the misfiring and carb-spitting was gone. So I am assuming that the fuel was indeed old and had deteriorated. It seems widely believed that gasoline deteriorates quickly when stored but definite information seems hard to come by. So far, I have found no information on the following: - In what way does gasoline deteriorate when kept in the fuel tank of a car. Chemical changes? Evaporation of volatile components? - What happens (or does not happen) in the engine's cylinders when the degraded fuel is used? I now have a quantity of gasoline that I can't use in the car. Somebody told me that I could get rid of it simply by adding it to the tank of a modern car that uses fuel injection, rather than a carburetor. Is that correct? My thanks for any information or pointers to where I can learn more.