Originally Posted by 06quad4x4
My father recently deleted his '11 3500 cummins with a smarty jr and flowpro test pipe. He went from 15mpg highway to 22.3 mpg and the truck only has 8,000 miles on it. According to most people cummins trucks will get better fuel economy once they're broken in. I say if the dealership is willing to do the deletes, go for it.
Same numbers from our 07...great mod!