Internal engine combustion generates the power your Toyota or Scion uses to run. Your original spark plugs generate the electricity that makes burning that gas possible. Without a set of factory spark plugs you can rely on, your ignition system wouldn't work, and that would mean a disabled vehicle. How do spark plugs work? It's simple: they trigger, igniting your engine's air-and-fuel mix and bursting its chemical bonds. This releases the necessary energy. Your engine pistons then fire, pumping back down and turning your crankshaft. This gets your vehicle's moving parts going. Over time, however, even high-quality spark plugs from an OEM like Toyota or Scion can decay. Plug leads can oxidize and widen and sparks can get smaller and weaker. The results can be an inefficient engine, misfires, or outright engine failure. Worse yet, when a spark plug goes bad, it can break. That can mean serious engine cylinder damage. Luckily, most spark plugs are made of high-strength metals and stand up to millions of ignitions, some with extended lives of 100,000 miles or so. So, it's easy to tell when to change spark plugs. Just ensure you aren't using them beyond their mileage limits. The question of what spark plugs to get is just as simple: the best answer is genuine Toyota and Scion. You can order them online, right from our auto parts counter. Buy now and you'll be repairing your ignition in no time!