Will upgrading to bosch platinum fours on a mostly stock motor lower gas mileage? A freind of mine drives a 00’ Civic and says that it lowered his gas mileage because the new spark plugs were burning the fuel too fast. also will going to the platinum fours decrease the chances of detonation?
-DB
bosch suck. cars run bad on them only cars they are good for is german. if your looking for plugs get ngk, they cost anywhere from $3-$7 a plug if you get the best. also for nitrous or forced induction they come in different heat ranges. 
I have been running Bosch +4 plugs for 2 years. They seem fine to me. My fuel mileage has been 30 to 36 on the highway for the entire time. Head wind, tail wind, up hill, down hill, weight, trailer, speed. Lots of variables.
your lucky i have heard horror storys :-o. I am glad you havent had problems they my be worth a try :? I like my ngk’s though.
NGK it is. Thanx for the help.
im running bosch P4’s with no probs’ if you plan on going spray dont get coated though