i am driving my 07 cummins 5.9 like a granny trying to get better fuel mileage, before i changed my driving habbits i was only seeing about 14.5 to 15 mpg. i was seeing around 20 with my 03, 6 speed. i didnt think they made that much of a difference but in any difference im thinking about getting the mp8 because i heard that they help alot but i dont want to ruin my transmission with extra power. i want to keep it going as long as possible. everything is stock with the exception of straight piped, and cold air intake. is there anyone else that is using the mp8 with a stock auto? and if so how is the transmission handling it?

 

Mp8 is a pressure box. You need a smarty or comparable tuner to boost your MPG.
Your tranny is at it's limit stock. Get a TQ and Valve body at a minimum. The MP8 is more likely to melt a piston before breaking your tranny!

 

I ran a MP8 with my stock trans, I just drove smart. I kept my foot out of it on full power, I mostly kept it at half power and when towing I turned it all the way down. I saw a gain of 2 MPG better, but I was driving very conservatively.