The old numbers are not used in the auto parts now. Except for Autolite and AC. NGK and Champions have part numbers that the counter guy needs to cross to so he can find the plug on the shelf. The minimum wage part timers may not know how to get your RN12YCs that are actually 404s. And the software is based on year, make and model. Asking for a BPR6ES without that information may get the "duh-duh" look.

Some of the old plugs, 55-51 Autolites and some on the non resistor numbers are no more. Race plugs are usually what you need for copper non-resistors..

Factory catalogs or websites will be helpful with numbers and what is still available. Have the part numbers when you go to the store.

Last edited by CMcAllister; 01/02/23 02:43 AM.
If the results don't match the theory, change the theory.