99 2500 Cummins MPG low?
 

I just bought a 1999 Dodge Ram 2500 Cummins, EXT Cab, Long bed, 266,500 miles, Automatic, 4x4. It has 4" straight pipe, Airdog 150 pump, and a BHAF. Other then that's it completely stock.

After I got it I did all the fluid/filter changes. I have finally gone through 3/4 tank of diesel and I calculated my mileage and It only came out to 13.1 mpg.

Would this be about right for my truck? There's no codes, and I did try really hard to drive it easy, but every now and then the pedal does get away from me. :humm:

Thanks,

seems low to me, when mine was stock minus the lift pump i was getting a little over 17. maybe needs valves adjusted. is it really chatty sounding?

Mopar1973Man's Dodge Cummins Articles - Valve Lash Adjustment

Kinda sounds chatty. I will adjust the valves this weekend. Being out of spec will cause that much of a mpg drop?

Thanks,

What's your rear end gears? And are you running highways or back roads?

and what tire size?

is it cold were you are?

winter mileage will be a few mpg lower than summer mileage in a 24v cummins. they use more fuel and retard timing to compensate for colder climate conditions.

wouldn't hurt to verify air pressure is ok in the tires and that you don't' have a dragging or sticky brake caliper(s). I would think you should be around 17 at least.

I run with 295/70/17 tires, winter, 3.73 gear, all town driving in a 6spd without a programer or tuner and get 11-13 MPG. This is probably due to the fact I drive a little fast, always have 1/2 ton of heating oil in my bed, and have a late 02' without the CAD, so it is always spinning my front axles. When I'm running highway at 55, getting about 16MPG. So it has a lot to do with your driving habits, speeds, and tires.

There is a lot of great ways to increase your milage. Airbox, free flowing exhaust, programer, injectors, tires, free spin hub kits, WaterMeth/Propane, tropper/tanneau cover, and if you do a LOT of interstate driving (75+mpg) a Gearvendor Overdrive unit.