As some folks will recall, I was skeptical of the claims made for iridium plugs for years. Early this year, Michael Morse talked me into trying a pair (NGK BPR7EIX). Eating a plate of crow never tasted better: although I didn't do Pete's meticulous charting, the iridium plugs provided faster warmup to steady idle, improved gas mileage, and a slight seat-of-the-pants gain in power. I won't be using anything else in future.