Something about engine spark plugs that rarely seems to get mentioned is indexing. What is it, actually? Should you index the spark plugs on your engine?

If you've ever seen a mechanic draw a tiny line on a spark plug before changing it, they're not performing witchcraft — they're indexing it. The idea is simple. Most standard types of spark plugs have ...

If you consider your spark plugs little more than disposable engine parts to be replaced for every event or two, you're missing out on a valuable engine-tuning tool. Not only can the correct plug ...