We may receive a commission on purchases made from links. When it comes to engine care 101, a spark plug replacement — also referred to as a tune-up — is an essential task. Spark plugs, as the name ...

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 ...

For hot rodders, spark plugs are often nothing more than inspection tools that reveal whether an engine is running too rich, too lean, or just right. Street guys look for a nice tannish-brown tint on ...