I've had the E3's in my truck for about 6 months now and I can't say they made a big difference, but I felt better throttle response. I mainly bought them due to their milage garuntee...I forget how long it is, but it was something like lifetime or 100,000 miles. Fuel milage might have went up a little bit, but I usually don't look at that...my right foot tends to get a little heavy here and there.