If your Cummins diesel engine is for everyday use and you don't tow this could probably work for you, but if you tow, even a light one (I tow one 21-foot trailer), this will cause you to be stranded on the side of the road overheated. With my stock fan and fairing, I could tow 65 mph on the interstate, and the engine temp never went above 195 degrees. First hike this summer after installing Flex-a-lite and the first steep climb. I used to just drive over the top and my temp gauge was 240, the 'Check Sensors' light was on and I had to slow to 40-45mph. just to keep the temp from going up to 240. It just doesn't seem to draw enough air to keep things cool, and with Cummins that shouldn't be an issue. As soon as I get home I'll go back to the OEM setup and try to sell this thing.