With the antiquated points ignition and, carburetor fuel delivery systems (both of which begin their gradual degradation until their ultimate failure due to normal wear and tear upon the first revolution of the crankshaft), these plugs will foul just as quickly as the original equipment plugs did.
With the advent of computer controlled electronic ignition and fuel injection, modern engines are not subjected to the problems associated with the old system, and therefore you can run plugs for pretty much the life of the engine. I have put 173,000 and 161,000 miles on two Dodge pickups on the original plugs. The 173,000 mile one developed a sloppy overhead cam chain and was sold at auction (still running, just a bit noisy when engine was cold) and the 161,000 mile one is still in service and runs like new.
Carl
Last edited by 52Carl; 12/04/2014 4:58 AM.
