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Q--I have a Jeep Cherokee 4.0 liter-engine that's approaching its recommended spark plug replacement mileage (intervals of 30,000 miles per the owners manual). I'm interested in replacing the standard plugs with a multi-electrode or split electrode platinum plug for three reasons: increased performance, increased fuel efficiency and extended spark plug life. In particular, I'm considering the Bosch +4 or Splitfire plug.
Do platinum plugs last longer than standard plugs and approximately how much longer under normal use? Will multi-electrode or split electrode plugs increase performance and fuel efficiency or are they a marketing gimmick with little incremental value compared to single electrode plugs? Do these plugs meet manufacturers specs so as not to void my base or extended warranty? Which would you recommend insofar as they are priced similarly?
A--Yes, platinum plugs last longer and that is how carmakers can boast 100,000-mile tune-ups (although I would not leave them in that long).
Multi-electrode plugs have some advantages during starting and at high speed. With several paths as an option, the spark has an easier time jumping although I am not thoroughly convinced that some designs are more than gimmicks.
I have not yet seen any brand of spark plug that will void the carmaker's, or extended, warranty. But you may want to read the fine print just in case.
Finally, I am reluctant to endorse any particular brand of spark plugs, but you can always rely on the long-established brands.