Hi Guys, Not a big sample size but I was a bit surprised i was under 12mpg. I only ran about 10 ggallons out of a full tank and refilled. So it could be wildly inaccurate. What do you guys get for mileage?

Don't have a Cummings Mopar, have a 5.4 Triton supercharged F150 supercrew, 12 mpg would be a 10 to 20% gain! LOL

Is that towing anything or unloaded? City, highway, or higher speed interstate? Seems rather low if unloaded, and doing mostly highway miles and it may be reasonable if towing something heavy or at high speeds.

Are you located in cold country? If so you have a couple strikes against you.

One being fuel blended for fridged temperatures reduces economy, secondly Diesel engines like heat.

My work truck is down roughly 20% during this latest blast of cold.

My 12 valve averages between 17-23 mpg, depending on what I'm towing, and how hard I'm pushing it.

Can you provide model year? I know various people who have Cummins Rams.

So many factors go into fuel economy but the fact that you’re talking about it says to me you aren’t pulling a heavy load or driving it like you stole it. That being said I would likely expect better from your rig. Check for boost leaks. Likely culprit will be the rubber couplings, they may just need to be tightened or they may have a hole. Several other things will contribute as well but with the age of that truck that’s where I would start. I like the silicone replacements if you do have to go that route.

Mine is a 2002 4wd quad cab long bed. Yes it is cold here. I am not driving it much at hiway speed. Mostly, I would say between 30-50 mph. Not towing. I have no idea what boost leaks are. The truck was checked out mechanically and repairs were made and service done. Has 240k on it.

Thanks guys.

quote:

I have no idea what boost leaks are.

I would imagine it's leaks at the couplings for the turbo system

12 mpg on that strikes me as very low. It should get in the 17-20 range empty and on the highway, maybe 15 fully loaded. I doubt if your measuring method is accurate.

(edited to revise figures a little)

This message has been edited. Last edited by: egregore,

Thanks guys. Egr, I think you are correct as your numbers are what I was thinking it should be as well. Appreciate it guys.

I have a 02 dually 24v and get at least 10 towing a 40 foot enclosed (aluminum) car trailer. On flat land more like 12-13. Without a trailer more like 15-18.
Have you ever had the injection pump replaced and do you have a fuel pressure gauge to measure the supply pressure?
When the feeder pump stops supplying the injection pump with at least 5psi under a load, the injection pump gets higher wear and will eventually fail. Before that happens the mileage goes down hill. There is also a circuit board on the pump that can go bad. Fuel pressure does several things besides just providing the fuel it runs on. Lubrication of the pump and cooling comes from proper fuel pressure and flow.
Do a search on that. There's all sorts of info online about those engines and the fuel system.
I bought a Blue Chip pump years ago that is optimized for mileage but also gets a bit more power. He has a lot of good info and diagnostic info on his site.
https://www.bluechipdiesel.com/

This message has been edited. Last edited by: 220-9er,

2005 Crew Cab/4wd/G56 manual here.

Not an apples to apples, I know, but I get around 12 in town and 15-18 highway (unloaded for both types of travel).

Not a totally fair comparison as it is old tech and lighter, but my brother's 1992 model gets 22 empty, around 16-17 towing a car on a trailer. After the intake heater (no glow plugs) light goes off, it starts faster than you can let go of the key. He says people are always bugging him to sell it.

My 2018 2500 gets 30 mpg at 55 mph. When new I saw 35 mpg, but with different tires and 50k miles I am down to 30.

quote:

Originally posted by old rugged cross:
Mine is a 2002 4wd quad cab long bed. Yes it is cold here. I am not driving it much at hiway speed. Mostly, I would say between 30-50 mph. Not towing.

ORC - I'm thinking that speed and fuel might be the cause of the low MPG. I'm assuming you're running a winter blended diesel.


My 2006 (3rd gen) 4WD SRW 3500 gets the best mileage in the summer if I keep it between 55-60ish, I can get 20+ all day long (not towing). Running at 75, that number drops pretty quick to 15.


I believe my overdrive kicks in right around 50MPH mark. I'm not sure what kind of mileage I'd be getting at average speeds less than that.


Winter blended fuel will drop my numbers down to 12-14 or lower depending what the blend is. Typical winter temps range -10F to +20F (although it was in the 30's today, just about shorts weather .


Length of your trips could also have an impact. In the winter months it takes a long time to get up to operating temperature (especially if I don't have the winter front in).


Short trips (I'm making an assumption with that one), lower speeds, colder weather and winter diesel I don't think I'd be too surprised with 12MPG.

Good to know SBF. Thanks guys. very helpful.

2001 Extended cab short bed 4x4 with Goodrich K02s.

I get 21-23 consistently for mixed driving.

I never really allow the engine to get above 2500 RPM and kinda drive like an old studabubba.

Your mileage is shit. I would check for turbo leaks, or failure of the turbo as well as fuel delivery issues. Investing in a fuel pressure gauge that reads pressure from the delivery pump is a very valuable investment for these trucks.

I would also make sure you aren't driving it on a ton of short trips around town, never letting the engine get up to full operating temp.

These old diesels aren't modern four bangers, and don't play well with many short trips / constant short cycles in cold weather. Buy a beater for your errands.