What is “indexing” and how much more power will I get? Indexing (AKA “degreeing”) refers to how the spark plugs are installed so that the ground electrode is oriented to face the intake valve in an effort to “open up” the spark to the incoming air/fuel charge. This is accomplished by placing a washer underneath the spark plug’s shoulder area (of a specified thickness) so that after properly torquing the spark plug, the electrode would be pointed in the desired direction, usually towards the incoming air/fuel charge from the intake valve. It is important to note that any power increase will be small and the results can only be determined after extensive dyno testing. It is generally a waste of time unless you have the training or the dyno facilities to document the results.

Do I need a colder spark plugs? A rule of thumb is one heat range colder for every 75–100hp you increase. In identical spark plug types, the difference from one full heat range to the next is the ability to remove 70°C to 100°C from the combustion chamber. The heat range numbers used by spark plug manufacturers are not universal, so a 10 heat range in Champion is not the same as a 10 heat range in NGK or in Autolite. When making the decision to change the heat range of your plugs, it is a wise idea to make changes in 1 heat range increments, checking all your plugs for suitability during your test. Vehicle modifications during the test phase of your plugs is not recommended as this may skew your results.

So really…do I need colder spark plugs? Probably not as in the end it won’t make enough difference to be felt. But if you want the bling of saying you have iridium one step colder plugs and you enjoy the work, knock yourself out.

Do I need to consult with my tuner about spark plugs? Yes. Items in your car that can be tuner specific: manual boost controllers, electronic boost controllers, upgraded wastegates, restrictor pills, wastegate helper springs, external wastegates (type/size/brand), spark plug types/brands/gaps, and injector types/brands/sizes. ALWAYS take your tuner’s advice on these matters no matter what the internet tells you!