Fast69Mopar when I bought the truck I was getting 12.6mpg. As of today I am down too 10.5 no matter if its HW or City. I have already replaced Bank 2 Sensor 2 for the O2 sensors. Scan tool has shown me nothing out of the ordinary. As far as highway driving speeds most of the posted speed limit is 70mph, so I am usually always 5mph over the posted limit. Most times the cruise control is on. I saw in another forum somewhere that a guy was having the same issue I am having. He stated in his post that his timing chains had stretched which caused the timing to retard, which gave him bad gas mileage. He said after he replaced the chains and quides that he was getting 15-17mpg HW. Makes no sense to me though, timing chains don't stretch.
4.7, 5.7, 3.9, 5.9 etc. timing chains can and will stretch, especially 4.7 chains. I have replaced way too many 4.7 timing chains along with tensioners and guides.
Does your scan tool have the data capability to show you the timing?
We could look at the base timing at idle and the total advance while cruising. If the timing was an issue we would see it in the data on the scan tool.
How many miles are on this engine?
Has the front cover ever been off? Or the rocker covers?
This is a two wheel drive model, correct?
What RPM are you cruising at while running 70mph?