You're ready to put new spark plugs in your car, but you have an essential decision to make first: copper, platinum, or iridium plugs? If you're not familiar with spark plugs or how they operate, that question might sound nonsensical. What do metals have to do with your spark plugs, and why should you care which type you use?
Ultimately, it all comes down to conductivity and durability. Your spark plugs need to deliver high voltage electrical arcs (that's the spark!) to ignite the fuel/air mixture in your car's combustion chambers. However, different metals offer different levels of conductivity and durability, making this choice a meaningful one that can impact your car's performance and efficiency.
How Do Metals Compare?
If you spend some time browsing auto parts websites, you'll probably notice that copper plugs are primarily associated with older vehicles or specialty applications. Meanwhile, you'll usually find iridium plugs in newer vehicles. Does this difference mean that iridium is a better conductor than copper? Not quite.
Copper is, by far, the most conductive of the three options available. As a result, copper plugs offer the most outstanding performance. Unfortunately, performance isn't the only factor that matters for your spark plugs. Heat and temperature resistance will also impact the longevity and durability of spark plugs. An inappropriate heat range can cause the plugs to overheat or quickly become fouled with carbon.
While iridium doesn't offer the same electrical conductivity as copper, it does offer drastically better heat tolerance. Iridium plugs also perform better than platinum plugs, which offer the worst electrical conductivity of the bunch, although they still outperform copper for heat tolerance and effective heat range.
Which Option Is Appropriate for Your Car?
There's a simple answer for choosing the best plug for your vehicle: stick with the option that it came with from the factory. Most manufacturers currently use platinum or iridium plugs. In general, you can upgrade to iridium if your vehicle uses platinum plugs, but you'll want to double-check that the heat range and gap are appropriate for your application.
While copper may look tempting thanks to its increased performance and lower price, copper plugs are often inappropriate for modern vehicles. The lower acceptable temperature range can ultimately lead to carbon fouling and a shorter lifespan, removing any potential advantages. However, if you drive an older vehicle that requires copper (or "standard") plugs, you'll generally want to stick with them.
Remember that your vehicle's manufacturer engineered your engine to work with specific spark plugs and spark plug materials. Although there are differences between plug materials, your car will generally perform the best if you stick with plugs that meet or exceed your original factory specifications.