The biggest improvement in spark plug technology came in 1985 when the first generation “long life” plugs with platinum or gold-palladium electrodes hit the market. Up to this point, electrode wear usually dictated when a set of plugs had to be replaced. With standard nickel alloy electrodes, the spark gap between the center and ground electrodes grows about .0002″ to .0006″ for every 1,000 miles of driving. After 35,000 miles of driving, the gap can grow as much as 0.015″ or more.
Every time a spark plug fires, the hot spark blasts a few molecules of metal off the electrodes. Eventually the point is reached where the ignition system can’t generate enough juice to jump the gap, causing the plug to misfire.
With platinum, gold-palladium and other exotic metals, electrode wear is greatly reduced. Most platinum plugs can go up to 100,000 miles before they have to be replaced. The same is true for plugs that use other exotic metals, such as iridium for their center electrode. Plugs with platinum on both electrodes (“double” platinum plugs) experience even less wear than plugs with only a single platinum or platinum-tipped electrode.
Long-life spark plugs drastically reduce the need for maintenance while helping to maintain like-new performance. Not having to change the plugs so often is a real savings, but it’s no guarantee the plugs will go the distance.
Spark plug manufacturers tout the advantages of their unique electrode designs, but regardless of the design, the purpose is to make it as easy as possible for the plug to fire reliably. A spark jumps more easily from a sharp edge than a rounded, blunt edge. So the more sharp edges it has to jump to, the better the odds of the plug firing under all types of driving conditions.
One thing to keep in mind with respect to performance claims is that no spark plug creates horsepower out of thin air. A special electrode configuration can reduce misfiring and the voltage needed to fire the plugs, but the spark only ignites what is already in the combustion chamber.
To burn off carbon deposits, the center electrode needs to reach about 700