Rick's Free Auto Repair Advice

Copper spark plugs versus platinum spark plugs

Should I use copper spark plugs

It’s common knowledge that copper plugs are the best choice for all engines. Right? Wrong. All spark plugs have a copper core. But “copper” spark plugs have a nickel allow tip fused to the copper core. That nickel alloy has the lowest electrical resistance of all the metals used for spark plug center electrodes. That’s why some carmakers prefer those plugs. But there’s a huge downside to nickel alloy tipped spark plugs; they don’t last as long as other precious metals.

Copper spark plugs wear faster that precious metal tipped spark plugs

Keeping a sharp edge and maintaining the gap are critical to producing a spark that’s hot enough to ignite the air/fuel mixture. The sharp edge of a nickel alloy tipped spark plug erodes at least twice as fast as a center electrode tipped with platinum. As the nickel alloy tipped degrades, it rounds off. The erosion also increases the gap. A larger gap requires a higher firing voltage which stresses the ignition coil(s) causing overheating and early failure. Because it take more voltage to fire across the larger gap, the spark duration is much shorter, resulting in poor ignition.

Lean burn engine switch to platinum tipped spark plugs

To lower emissions, carmakers switched to leaner mixtures. To ignite those leaner mixtures, engineers switched to distributorless ignition systems (DIS) to provide higher firing voltages. In a DIS system, the spark fires from the spark plugs center electrode on the firing cylinder. But to complete the electrical path back to the ignition coil, the return electricity must jump from the SIDE electrode back to the center electrode on the firing cylinder’s “partner.” According to Autolite engineering team, “although copper spark plugs may function well initially, they are not designed to handle the needs of a DIS engine and will likely fail prematurely.”

The engineers add, “Copper core single platinum spark plugs are not designed to withstand this reverse polarity firing and will suffer premature gap growth due to center electrode erosion. Gap growth will stress ignition system components by requiring more voltage to fire,” said Dave Buckshaw, Honeywell CPG trainer for the FRAM® and Autolite® brands. “This degradation can be noticeable as soon as 20,000 miles after the plug is installed.”

Buckshaw adds that many consumers don’t realize that very few new vehicles still use copper core spark plugs and those that do – like the Chrysler® 5.7 Hemi V8 – specify a 30,000-mile spark plug change interval.

Double platinum spark plugs replace copper spark plugs in DIS ignition systems

Double Platinum plugs are specifically designed for engines with DIS systems and are 30 percent more durable than the average of leading competitors. The platinum-to-platinum firing offers virtually no gap erosion and performance that lasts for up to 100,000 miles. Autolite’s proprietary platinum alloy and welding process on the Double Platinum plugs provide superior engine performance, longer life, improved fuel economy and easier starts.

Autolite XP Xtreme Performance® spark plugs designed with an iridium-enhanced .6mm finewire are also compatible with DIS engines. These ultra-premium plugs require less voltage to fire and have a faster flame kernel growth in the combustion chamber resulting in a better, faster, more efficient burn compared to the .8mm finewire, multi-electrode design and standard plugs. Not only does this increase fuel economy, but, according to Autolite engineers, igniting more gas and air mixture inside the cylinders will result in improved throttle response and acceleration.

Carmakers switch to iridium on coil on plug ignition systesm

To produce maximum firing voltage, an ignition coil must have enough time to create a large magnetic field. By switching to coil on plug ignition, carmakers can allow each coil enough time to build that large magnetic field. When the field collapses, it can produce a much higher firing voltage with a longer duration to ignite the leaner air/fuel mixtures. To handle that higher voltage and maintain a sharp edge and proper gap, carmakers uses iridium tipped center electrodes and iridium tipped ground electrodes.

Never use a copper spark plug in a coil on plug ignition system unless it’s specifically recommended by the carmaker.


© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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