Originally Posted By: user52165
Why copper? Platinum or iridium are usually best.
What application and what is OEM?
Copper is best, platinum and iridium last longer.
As for interval, 30,000 miles is the standard, but if they are easy to get to, I pull them at 15,000 and check, and maybe replace.
If using a performance ignition or just a high horsepower vehicle, I would check/replace every 15,000.