Most IKBA regulars will know of additives used by petrol companies over the years. National Benzole Mixture provided another example.
(National was also partly responsible for introducing The Smurfs to a blameless UK public .)
The launch of "Baxtrol" in 1949 - when petrol was still rationed - caused a minor sensation.
Finally, there was that so-and-so petrol station owner who was diluting his or her fuel with water at a Gulf station in East Cheshire last November. Water-injection is all very well under the right circumstances, but the mixture didn't do my old bus too much good. It got me home, though.