I want to get some platinum plugs. So I went to the store and there are so many. I have an 04WJ 4.0 . I saw the Autolite ones and the Bosch ones with the 4 contacts. What is really the difference besides about $8 a plug? I need some assistance. The reason I want to change is I am starting to get a knock and poor gas mileage, my fuel pump is new so I know its ok. I just hope its not injectors. thanks
IF you decide to go with platinums DO NOT buy the gimmick plugs with multiple contacts. They are useless. Electricity will always follow the path of least resistance so no matter how accurately they manufacture the plugs, one contact is always closer than the others and therefore only one will have spark. In many cars they require platinum plugs as they were designed for them. With trucks (especially chrysler) most just use standard copper from the factory. plat plug upgrades will never give you much of a performance boost, just buy a better quality copper plug.
1999 WJ Grand Cherokee Limited 4.7l V8 164k
2012 KK Liberty Limited 3.7l V6
2009 G8 GT 6.0l V8
The reason some cars specify platinum plugs is that they last longer. I know for Subaru dohc engines the plugs are horizontal and a MAJOR hassle to change due to there only being ~2" space between the heads and the unibody. The SOHC ones are angled, and way easier to change.
My 01 Impreza went to the shop 1 time for a ticking noise from the heater fan. My 98 Impreza went to the shop 1 time for gear oil dripping out the splines on the front diff onto the exhaust. Both of those were bought new, and I put 33k or so on the 98 in a year and 60k on the 01 in 2.5 years. My 99 WJ (first one) was in the shop about 20 times in the first year I owned it.
I have another thread due to a missfire in the engines section.
I put AC plugs in my friend's Jeep as Champions weren't available. My preference would have been Champion Platinums because I have had good luck with them and because it is not my ride so who knows when they would be done next.
The other available choices were Autolites or Bosch.
The origional plug for this engine is actually an NGK. The origional plugs in that 4.0 were badly worn with 66,000 mi on them.
I will have to consider the coppers for my own rides in the future.