POWERSTROKE or CUMMINS

I had an 08 Dodge with the 6.7 and the auto and I really liked the truck but I never got more than about 10-11 miles/gallon in it and that just doesn't cut it. I had an 07 Dodge with the 5.9 and an auto (that I should have kept) and would consistantly get 15-17 which isn't great but is atleast respectable. I have had a 99 dodge auto for little while that I liked alot and was a good truck and I had a one ton dually six speed 02 model that I really liked except for the fact that it walked all over the road and while pulling a D3B it was a little exciting at times. I truly think if someone gave me a bunch of money I would find a unbelievably clean 5.9 12 or 24 valve with a 5 or 6 speed and put a fuel pressure guage on it and drive it till it fell apart. I found one the other day except it was an auto but it had something like 32K original miles and was an 01 model SPOTLESS and they wanted $19K for it. That truck would last a person a long time and run better and get better mileage than anything new out there. I think I would try a Dirtymax if I was going to drop $50K on a new one....