Jim B,
Mulino, Washington
I was a little leery about it, but it was the best thing I did for my motorhome. I have a 330 Cummins in my bus and I can go up the mountain passes about 10 miles an hour faster than before. Seems to be getting better fuel mileage too, but haven't checked it yet. I'm impressed, didn't think there would be that much of a difference.