Why Buy Expensive Platinum Spark Plugs When Cheaper Copper Ones Exist?

The reason why you should always stick to the manufacturer-approved spark plug type has to do with the ignition system of your car's engine. Newer vehicles with electronic distributor-based ignition systems often run on longer-lasting platinum plugs. These spark plugs have platinum discs attached to the tip of the center electrode. Since platinum is a harder metal than the nickel alloy of copper plugs, they wear out at a slower rate and can last 60,000 to 100,000 miles.

Moreover, platinum burns hotter and has a higher melting point, giving it the ability to burn off carbon deposits and resist fouling. You should avoid downgrading to copper plugs if your vehicle runs on platinum plugs, since the former will wear out sooner and will require more frequent replacements, and it could cause performance drops and engine damage.

Vehicles with electronic waste-spark ignition generally require double platinum spark plugs. Engines with waste-spark ignition (like the venerable Mitsubishi 4G63 that powered most Lancer Evos) need spark plugs with platinum discs on the center and side electrodes to handle the reverse spark that happens when one cylinder is on the compression stroke and the other is on the exhaust stroke (which is one of the four engine strokes in an internal combustion engine). In that stage, the spark travels from the side electrode to the center.

If your goal is to save money, you may end up spending more if you insist on using copper plugs in an engine that requires platinum. Platinum spark plugs cost around $6 to $8 each (which isn't significantly more than copper at $5 each), and they can last three to four times longer. If you use copper, then you'll most likely end up paying more in the long run, due to the more frequent replacements.

Copper spark plugs cost about $5 each and are typically standard in older vehicles with engines that run on lower-voltage distributor-based ignition systems. Since copper plugs run cooler (yes, spark plugs come in hot and cold varieties), they're also great for high-compression engines or turbocharged motors that generate more heat during combustion.

Despite their name, copper plugs have a nickel-alloy electrode welded to the solid copper core, and it's all about making the the copper core last as long as possible. Unfortunately, the major downside is that copper is a softer metal and wears out sooner than platinum-infused spark plugs, and they typically need replacing every 20,000 to 30,000 miles.

If the vehicle owner's manual recommends copper plugs, stick to it, and resist the urge to upgrade to costlier platinum or iridium plugs. Why? Some engines are engineered to run specifically on copper plugs. And for some applications or certain makes and models, copper plugs are classified as high-performance plugs, mainly for their inherent ability to route more heat out of the combustion chamber.

Although there are options to upgrade from copper to platinum or even costlier iridium plugs, the important thing is to select the right voltage, heat range, and size to ensure direct compatibility and problem-free performance. Persistently running an engine with the wrong spark plugs can result in misfires, excess carbon deposits, poor fuel economy, and expensive repairs.