Just my 2 cents(for what its worth) back in my hot roddin days, I replaced plugs like they were going out of style. Both Autolites and Champs were the worst about fouling. One day I decided to change it up and bought a set of NGK at that time (20 yrs ago) they were cheaper than the others, not as well known. Now they are a little better known and run about the same as the big name, but I have never had one go bad out of the box. I use them in everything that has a motor and will never buy the others again, just a personal preference thing (IMHO). I believe the PN. for the 2.5 is 2248 (NGK UR55) for the V-power copper, about 2.10 ea. at Advance.