Hmm, I've replaced the wires like a month ago or less (was my first try, forgot to mention it) and the plugs, I changed them around 70-75,000 miles (car has 94,000 miles on it now), but my speedometer is 10mph off so Im sure its added more to that. I don't think it was too long ago since I had the plugs replaced, will have to look at papers to see when.