I just stumbled across this technical paper that is devoted to explaining about anything you could ever want to know about gasoline. I haven't figured out the header info but it seems to indicate an affiliation with MIT. If you want hard technical info on things like where EXACTLY gsoline comes from, the precise nature of the incremental changes in gasoline from the 1890s to the present, what causes valve seat recession, and much, much, more go here: http://www.moparpages.com/faq/Gasoline_FAQ_Part1.txt The valve seat recession info is on page 4: http://www.moparpages.com/faq/Gasoline_FAQ_Part4.txt There is a LOT of info here. It would take hours, maybe days, to read through it all. Have at it! Pete in PA