That's an over-simplification.greasefingerss wrote:The heat index is the only important factor for spark plugs. If the heat range is correct then it does not matter whose plugs you select.
It's important also to make sure the plug is the correct model for your car. I've seen people use plugs that were the correct heat range but with the wrong reach and damage their engines.
Also, as I said, it's possible to use the right heat range and still have a problem with the plug. Platinum plugs with the right heat range have disintegrated in 951 engines, Plus 4 plugs have a tendency to ground-out on the 944's cylinder head, even with the right heat range... I can go on.
Brand is largely unimportant, but there do exist compatability issues with certain brands or types of plugs and certain engines.
Also, "Splitfire" brand plugs are pretty much universally junk. In general, sticking with Bosch, NGK, Champion, AC Delco or Autolite is safest.