I changed the plugs in the XJ a few days ago. I usually go with Bosch Platinum, which were in there, but I decided to try Bosch Platinum 2's. The weird thing is that they have 2 electrodes and don't need to be gapped ever. I don't understand why. I don't know if it's just a matter of new plugs OR if the Platinum 2's make a difference, but 4.0 runs much smoother now and seems to have more power.
http://www.boschusa.com/AutoParts/SparkPlugs/Platinum2/
Anyboday else using them or can explain how 2 electrodes don't need to be gapped?
http://www.boschusa.com/AutoParts/SparkPlugs/Platinum2/
Anyboday else using them or can explain how 2 electrodes don't need to be gapped?