I have a 2008 EX-L. My plugs fouled at 110K. Keep in mind I changed the oil with full synthetic religiously every 4k miles. So I was very surprised to have engine issues. Put a muzzler on right after. Just drove the car from Atlanta to Chicago and back with the muzzler. It drove better than brand new. Not a single issue. I did not see any change in mileage at all. Matter of fact I think I got better mileage. Smooth...powerful...wish I had discovered this device sooner.