I have a 2006 ram quad cab 4x4 with cummins 5.9 with 85k on it. I have owned it for 6 months. The mpg indicator says I am averaging 21.9 mpg and when I do the math I come up with 16.9 mpg. I can see it being a little off but that is a considerable amount and that is mostly highway driving. I am wondering if the transmission has anything to do with it, because if the truck has not been ran for a day it takes a few moments to go into gear, both forward and reverse, but after it starts moving it feels fine. Also I was towing my boat and forgot to put it in tow mode, it weighs about 7000 lbs, and it towed it fine until the last hill and it got a trans overtemp light and started to slip. I let it cool down and it works fine and towed the boat again with tow mode and had no problem. There is no smell in the fluid and level is good. I am wondering if the bands could need adjusting, because I don't think the trans should have overheated on one hill about a mile long. I also read somewhere that the trans cooler flowback valve could have something to do with morning transmission engagement delays.
Any help would be appreciated, Thanks.