Never tested it, but from what I read and talked to friends who own them, they are governed at around 116 mph. Part of the reason why I get good mileage is the fact that I live in a very rural area and I can accelerate with ease. I drive like this because I'm on a tight budget right now with going to college, and I can't afford to put on new tires very often, nor can I afford to fix parts on it and pay the high gas bill. The friends I have that have these 3.5L powered Intrepids get mileage around what I get. The tachometer stays under 2k rpms at all times, including acceleration. I tested out different fuel stations (BP, Mobile, Conoco, Phillips 66, Casey's, F/S, MFA Oil). I found that I got the best results with F/S and MFA Oil, and found that I got the worst results from Casey's. The K&N added somewhere around 2-3 mpg for my car, however it varies from one vehicle to another what results you will get.

Most of these roads are pretty flat, at least flat enough that the torque converter doesn't unlock, nor shift out of overdrive. It runs at about 1600 rpms at 55 mph, 1750 rpms at 60 mph, 1900 rpms at 65mph, 2100 rpms at 70mph which are my normal cruising speeds. After I get out of college and get a good paying job, I'm going to get a more powerful car, hopefully a Challenger with a HEMI to make up for all the fun I have missed out on. Don't get me wrong, I still have my fun like beating Honda Civics, older Mustang V6, F-body V6, and cars driven by people with a bigger ego than a brain to know my "family sedan" can kick their butts in acceleration. I love that expression they have on their face when I beat them. Of course, I pay for it later at the gas pump.