platinum spark plugs or oem?
I just replaced the original spark plugs in my 2006 Jeep Grand Cherokee 4.7 with 54000 kms. It appears to be more responsive. The dealer wanted their service department to do the work and charge me a crazy amount for this. He even said that unless the plugs were replaced at the recommended mileage even though I put platinum plugs in, it could void the power train warranty. Also should I replace the difs fluids with synthetic (the Jeep is never really driven off road)?
Newer cars have tighter tolerance engines that can benefit from synthetic oil. So if you can afford it use it. Just make sure to use a quality "full" synthetic. You will get less internal wear and a very small increase in fuel mileage. And as for the the diffs, synthetic fluid can make them run cooler and last longer.
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