Lol please don't wait until 100k+ to replace the plugs, I say 75k is a good enough time, even at 60k with the serpentine belts ! Can't be too safe but at 20k, your engine is still a baby
72k on an 09 328 lol and I'm barely about to replace my spark plugs! Depends on your driving as well and how much you do. I have 3k more to go before I restore the power and efficiency back to the motor
