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 ...

After 152,000 miles, how much power does our E92 M3 still put down? We take it to the dyno for a real-world test and swap out the spark plugs to see if we can regain any lost performance. Watch the ...