I'm not a chemist, but I think it is a waste. Lots of folks here have driven their Imperials on unleaded gas for a long time and had no trouble. If the car doesn't run right, or spark knocks there is something else wrong that needs to be fixed. Paul In a message dated 5/24/2004 11:48:35 PM Eastern Daylight Time, abungaro@xxxxxxxxxx writes: > I own a 67 Crown convertible > Does anyone know if adding a lead additive (into a full tank of gas) >everyother fill up or or once in a while is helpfull or beneficial for the >engine and or performance?? Is it good--or is it just a waste? > I always use premium grade (and go to different gas > stations) > THANKYOU > ANTHONY BUNGARO