I have seen so many posts on what spark plugs are good and bad that I decided to look into the concerns. It is suggested that the NGK plugs are the only good plug for Jaguars. I am going to tell you that I am a long time user of Bosch plugs and do not hesitate to recommend them in any Jaguar. In the past I had defended my position that they are not a problem and that I felt that the problem has been with the application. In my quest to find out why all the hoopla I found out that both plugs are good, it is in the application that is in question.

Listed below are several links / reading material that should help in understanding spark plugs, proper gaping and temperature rating. It will also tell you the proper application based on the driving habits and performance demands and how to make the proper selection. My experience has been not to depend on the recommendations of what a 18yr old cashier at the local parts store. Do your homework, know what you are getting and why.

Never assume that the gap of your plugs out of the box is correct for your car. For the proper gap, go to your Vehicle Specification Book. You can find it on this forum or on my page under Electrical, OBDII codes, Tech Guides & Spec Book. When installing your plugs use anti-seize and be sure to properly torque the plugs. You do not want to overdo it and brake the plug and you do not want it to loosen up as you are driving.

I hope the information listed below will help you understand that the proper application of spark plugs for your car.

Spark Plugs
Bosch spark plugs - pro and con
Bosch Platinum vs. NGK Platinum Spark Plugs
Spark Plugs and Spark Plug Wires - Facts & Repair Advice
Spark plug - Wikipedia, the free encyclopedia
Spark plugs FAQ
FAQs

 

Great info to post of others...

An additional caution if I may. Owners should keep in mind that all torque specs are always on "clean and dry" threads. When torquing plugs with anti-seize, you should be using 15%-20% less than the specified value as the compound will act as a lubricant.

Another little known fact is that on older cars using carbon core spark plug wires can lose efficiency in as little as two years. The constant thermal expansion and contraction inside an engine bay creates micro fractures in the carbon core. The HV now has to arc across those micro fractures as well. I've opend a few hoods in the dark to watch a very cool light show of the wires arcing along their length.

Vince