Something about synthetic oil & the blue bottle... if you don't have a near perfect ring seal or good oil control, it just kills plugs. We were playing with a BBC pick up last year, ran 9.90's & needed a oil change. Put in Mobil 1 & started killing plugs. Changed everything, fuel, plugs, timing, nitrous.. nothing. Went & changed back to Castrol... 9.87 all in the same day.