I bought a set of 4 spark plugs for my brother's 1996 Toyota Tercel (0-60 in 4.5 seconds, quarter mile @ 12.9 seconds in case you were wondering......ha ha ha bad joke).
The ones given to me at the NAPA auto parts store were NGK V-Power plugs after I told them what kind of vehicle it was.
Well, after we finished installing them, we noticed a small warning on the engine block indicating to only use double ground electrode spark plugs. I've never heard of these...and the ones we installed were the usual single ground electrode plugs.
My questions are, what are these double ground plugs, why/when are they used, and is it safe to keep the single ground plugs we put in?