Assuming the majority have switched from points to electronic ignition. How often should the plugs be changed? Years ago I increased the plug gap to .035" and changed plugs at 10K. Didn't notice a decrease in performance as much as a drop in fuel economy. Usually got my money back for the plugs after the first or second tank of gas. Now that we have Platinum and Iridium plugs what should the gaps be, and how often should they be changed? Are the Iridium plugs worth the extra money, especially considering how easy they are to change?