I have a stock 2008 Ram 2500 with the 6.7L Cummins that has gradually lost MPG as I put more miles on it. I currently have 82K on it and have kept it regularly maintained at the dealer. It seemed that on the hwy I used to get 20/21 mpg and towing my 9000lb travel trailer I would get 12/13 mpg. I run at 1800 rpms which is equivalent to 75-79mph on the hwy or 65-69 mph when towing.

Lately, I have seen the mpg slide to 17/18 mpg on the hwy and last week I towed my trailer and only got 9/10 mpg. Still running at the same rpms as well.

I have only had regular oil and filter changes, but I did have the turbo replaced under warranty about 10K ago. Still seem to have just as much power as usual to climb a hill if needed.

Any thoughts of what could be dragging it down?

 

your emissions controls are what drags the economy down.


if you wish to keep it legal for emissions still, get yourself a pyrometer on there and then drive the truck and get that pyro to read and hold 1200* for as long as possible. (take it up some mountain passes pulling as heavy as you can and work the hell out of it.)

that will help burn off excess soot collected in the DPF.

or if you want to illegally fix it which is the better choice if you don't have inspections or emissions testing....

get a DPF and EGR delete programmer, and remove the DPF from the exhaust.

you will instantly regain power and lost fuel economy and likely see an improvement in fuel economy.

 

Thanks. This seems to be the consensus everywhere I ask.

 

yeah, as long as those emissions controls are on there, the EGR pukes exhaust back through the intake which will eventually clog it up, and the DPF catches soot and doesn't let it exit. it also works like a catalyst but it needs high temps to burn off the soot like a catalyst. so if the temps don't get hot enough it won't burn off the soot and will continue to cake up and clog more causing severe restriction in the exhaust which will hurt economy and performance.

long as the dpf and egr are on there, you need to run the truck hard and drive it like you stole it.

soon as you delete those items, it will run like a champ whether you are hard on it or baby it...