The Differences Between Spark Plugs

Did you know that there are different types of spark plugs? It's OK if you didn't. Most drivers have no idea about the variety of plugs or heat ranges in spark plugs. In fact, that is often the one place where DIY enthusiast get a little flustered, especially if they start reading hyped up information about how one plug type is superior to others. The truth is that every spark plug type is designed for specific purposes and engines, and the best way to identify which plug is right for your vehicle is to review your car's manual.

For the savvy DIYer, who has modified their vehicle's engine, it is possible that you might require a different spark plug than what your manufacturer recommends. Although, it is unlikely that you will need one with a different heat range. Therefore, if you would like to try your luck with an upgraded and updated spark plug to see if there are any performance benefits, then you will first need to understand the critical differences between the four most common types of plugs.

Important Facts to Consider

There are a few critical facts to consider when you start shopping for a spark plug replacement. First, you want to find a plug whose electrode will maintain its shape for the longest distance. Shape matters because sparks jump from sharp point to sharp point, meaning that they travel from the center to the side of the electrode at peaks. As electrode surfaces wear away, the spark becomes less efficient.

Second, when discussing voltage, the diameter of the center electrode is critical. Basically, the larger the diameter of the electrode, the stronger voltage required to ignite the spark and vice versa.

Last, you need to understand the heat ranges. The ignition temperature for the air-fuel mixture in your car is absolute, meaning that it will not change. Indeed, finding plugs with a higher range than suggested by your manufacturer might increase performance marginally, but you run the risk of the spark plug masking possible ignition issues. Therefore, it is always strongly recommended that you stick to your vehicle manufacturer's guidelines when it comes to spark plug selection.

Four Types of Spark Plugs

When discussing the most common spark plug types, you are primarily talking about four models of plugs: copper, single platinum, double platinum, and iridium. While the variety might be confusing, especially when trying to determine which plug is best for your vehicle, each spark plug has its pros and cons. Therefore, to figure out which is right for your situation, it is beneficial to discuss each type in depth.


Copper Spark Plugs

Copper spark plugs can be slightly confusing in their description because while the core is made of solid copper, the center electrode is actually nickel alloy. However, beyond the bait and switch of the name, the plug also boasts the largest diameter electrode, which means it requires a higher voltage than most other plugs. Additionally, because the electrode is made of nickel alloy, it tends to wear out faster than other materials. While it might seem like these things are negatives, which some are, the copper spark plug is still the go-to plug for most combustion engines, and while it is true that you will have to replace these plugs more often than others, they are generally less expensive. As a result though, the general rule is not to use copper plugs in DIS or COP ignition systems because they wear out too quickly.


Platinum Spark Plugs

A single platinum spark plug is similar to a copper spark plug, but instead of a nickel alloy tip, it has a platinum disc welded to the center electrode's tip. Platinum is a more durable material than nickel alloy, which means that it lasts longer, typically 100,000 miles. Also, because of the increased heat of platinum plugs, they do not tend to get as mucked up with spark plug build-up and fouling. These plugs are typically best used in newer vehicles with DIS systems.


Double Platinum Spark Plugs

Double platinum spark plugs were designed for waste spark DIS systems. Essentially, during the compression stroke of the ignition process, the spark jumps from the center to the side electrode. Then, for the electrical pulse to return to the ignition coil pack, the spark jumps backward from the side to the center on the partner cylinder, which occurs on the exhaust stroke, wasting the spark. These plugs work exceptionally well, but they should only be used in systems that specifically require them.


Iridium Spark Plugs

Single iridium sparks plugs are typically considered the most efficient spark plugs available and are often required for newer vehicles with COP ignition systems. These plugs last at least 25% longer than platinum plugs, and they have a smaller diameter electrode which means they require less voltage to spark. These spark plugs indeed cost more than other plugs, and while it might be tempting to swap them with more affordable options like copper or platinum, neither of these materials will perform as well in a COP system.

Know Your Owner’s Manual

The variety of available spark plugs can indeed make shopping somewhat confusing. However, there is a simple way to decide which plugs are right and best for your system, read the manual. Every owner’s manual will specify which type of spark plug is right for your vehicle and ignition system. Don’t assume to know better than the manufacturer. Granted, if you have performed extensive modifications to your vehicle, then you might have some wiggle room in your selection of spark plugs.

The four spark plug types addressed in this article have engines that they were designed for. For example, copper plugs are often used in older, classic combustion engines whereas platinum and iridium are now the preferred models for DIS and COP ignition systems. However, despite the general information provided here, the best resource to consult before going spark plug shopping is your car’s owner’s manual. Therefore, don’t assume one plug is better than the other, look in your manual and buy the plug that is specified for your make and model.

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