Another one of those pleasant expenses with the XF: 12 plugs at $12 bucks each. $144 just for the plugs...oh, brother! True confessions time and please, don't jump all over me but, I have never changed the OEM plugs in my cars in probably 30 years. If this was causing a problem in any of my cars, "they never complained." Years ago I had a Subaru that had over 120K miles and it ran like a top; I didn't fix what wasn't broken.