One of the most important auto parts in your car engine are the spark plugs. They ignite the fuel mixture from the carburettor or fuel injectors. Sparkplugs can wear out over time so it is important to replace them once the electrodes become too thin. However, even with new spark plugs it is essential that they be properly gapped. If you buy a set of sparkplugs at the Auto Parts Store they are relatively easy to install. But make sure the first thing you do is set the gap using a spark plug gap gauge (in the UK we call this a "feeler gauge".)
There are some great You Tube videos on spark plug installation (see below). The main tool you need is a spark plug socket for your ratchet wrench and more than likely an extension bar for reaching deep into the spark plug sockets in the engine's cylinder head. A universal swivel adapter will also be useful. Detach the high tension wire leads carefully and inspect the rubber insulators for cracks or splits that might allow the spark to short out on nearby metal. Spark plugs generally should be checked as part of every 30,000 mile tune up. Slightly dirty plugs can be sandblasted clean, though most auto mechanic shops will replace them given that a set of spark plugs for a V8 should cost under $50 (The labor cost would be more than that so there's a case for installing the plugs yourself)
Check your plugs when you remove them. If one is dirtier or more fouled than the others it may be an indication of a split exhaust valve, worn valve guides or improper fuel mixture. Build up of deposits on the electrodes is a sign of "bridging" or pre-ignition, symptoms you should talk to your mechanic about as you may need your engine timing or fuel mixture adjusted. On a two-stroke motorcycle's spark plug an excessively wet plug is a sign your carburettor jets are set too rich resulting in smoky exhaust and fuel economy that is likely less than optimal.
In the world of auto parts there are myriad selections of spark plugs, most from heavy hitter companies such as Champion, NGK, Autolite, Denso and Bosch. Over a hundred years of racing and consumer motoring, spark plugs have evolved and are much better engineered. New spark plug innovations such as Platinum and Iridium plugs are now popular. Circuitry too has improved and the Pulstar Plug uses a capacitor to store electricity, releasing it much faster in a powerful million-watt pulse of energy. Pulstar claims more horsepower and better fuel economy from the pulse circuit technology.
Splitfire’s new Dual Mag Sets use magnetic suppression core conductors which are more suited to high performance cars and off road trucks.
Overall, buying spark plugs is a trade off between price and performance. Some plugs are designed for longevity, others for anti-fouling in low quality fuel environments and many for all out performance. The more you pay the better plug you get. That's not to say cheap spark plugs are bad. It's more about whether you're driving an old workhorse truck, a new BMW sedan or a Kawasaki super bike. Buy the plugs according to the performance you expect from your vehicle.
We can safely say purchasing a good set of spark plugs is a great investment. Do you really want to be stuck out on the lake with a fouled plug in your outboard motor? Be yanking on a cord for ten minutes trying to start your lawn mower? Or using more fuel on a commute to work than you need to? So pick a good brand, make sure the gap between the Ground electrode and the Center electrode is at the recommended factory setting, and you can forget about your plugs until the next engine service. Enjoy a safe and reliable trouble-free ride!