Sorry about that last one!
About a month ago, I "invested" in one of those "multiple fluid treatment kits" (has 3 or 4 different "miracle " fluids for gas, trans, steering etc..about $30+ at local auto stores and guaranteeing longer life and better mileage) for my 65 Le Baron.
Had a hell of a time starting it up each time for the entire tank full of gas after I poured it in.
No real effect on the other equipment (knock wood). But once, while trying to get it started I think I blew something in the engine because one of the cylinders or valves (you can hear only one) occasionally knocks and especially when accelerating now.
I will never do that again. The fuel (especially some the high-end and high octane brands) available at most stations have plenty of additives to keep most fuel systems clean.