What can I do to improve the gas mileage on my 2009 Dodge 3500 Quad Cab Cummins?

I would like to know if there’s anything I can do to improve the gas mileage on my 2009 Dodge 3500 Quad Cab Cummins. I took it on a long trip about a year ago (roughly 3000 miles round trip) and I only got 16 miles to a gallon, which was 6 miles less than what the previous owner had told me when he drove it down to Calif. and back. Any information leading to improving the gas mileage on this vehicle will be greatly appreciated. Thank you kindly.


I have an extremely hard time believing anybody ever got 22 mpg highway on that truck

It’s basically a huge work truck, for pity’s sake

Sorry if that’s not what you wanted to hear

16 is about what I would expect, out of that truck, There are no EPA estimates for 1/2 and 3/4 ton trucks but CR was only able to get 14 MPG out of the last one they tested, so I would I would guess that you’re getting about what the truck will do.

Also, since this vehicle doesn’t use gasoline, the more accurate term would be “fuel mileage”.

Agreed. You might also take the rear axle ratio into consideration and whether or not the seller of the truck was fudging the numbers a bit.

There is nothing you can do. Your fuel economy is excellent at 16. Previous owners will swear to anything and probably never even check their own stories. You can’t really lie if you don’t really know.

The old 12 valve 5.9 L Cummins could achieve 20 MPG at 60-65 miles per hour.
The common rail 5.9L (2003-2007) Cummins was good for about 18 MPG.
The 6.7 L Cummins will get 16-17 MPG. These values are without towing.

There are companies like Bully Dog that offer “tuning modules”, exhaust systems and other performance equipment but unless your a high milage rancher or commercial driver the cost of the modifications will never be recovered.

If you could gain 1/2 mile per gallon, on a 750 mile per day drive you would save 1.425 gallons of fuel each day. A Bully Dog tuner costs $700.00

The best way to save fuel is to slow down. On rural highways I set the cruise control @ 70, SUVs and pick ups pass me at 85 MPH, with trailer.

Drive slower, coast towards red lights.

“I only got 16 miles to a gallon, which was 6 miles less than what the previous owner had told me…”

If you believe everything that somebody tells you when that person is selling a used car, then–unfortunately–you are being very naïve.

As the others have said, 16 mpg is the best that you will ever do with such a big, heavy truck designed for work situations. This truck was designed for heavy hauling, not for good fuel economy.

I am with @BLE. You want best mileage ? Drive 55 or less. Maybe the owner did get 6 mpg better. But sellers will only tell you the bet conditions if they tell the truth at all. Better, like mid summer at 45 mph going downhill.

Leave the truck in the driveway and take something else. That’s all I can think of.

22 mpg? Downhill with a tail wind and coasting…

Have you tried going 55mph? If I go 55-60 on the highway in my Prius Wagon it will get 48-54mpg, at 70 it drops to 42-45. Same difference in your truck.

What you want to do is hyper mile, my guess is you don’t actually want to do this, but to get better mileage you will have to. There is a Guy Named Diesel Dave on the ecomodder forums who gets great mileage with a big diesel dodge.

The only way you will get 22mpg highway is by going 55mph, and doing some mods. Some people here on the forums will scold you for going the speed limit so don’t let them know…

Here is good thread about truck aerodynamics, Does that truck look like a big prius with the special cap on? Theres a reason priuses are shaped the way they are.


Diesel Dave claims to have gotten 50mpg with hid big ram over a 24 mile commute, My guess is you won’t want to drive that way, and Im not sure I believe his claim.


Get a smaller truck.

If you believe there is something wrong that is causing this, and it is abnormal for your truck based on passed experience, I’d start with removing the EGR and seeing if it is stuck slightly open. A fouled EGR due to carbon deposits isn’t unusual at all. And it can markedly lower fuel economy. Removing and bench testing the EGR on most vehicles isn’t usually too expensive, so for the best bang for the buck, that’s where I’d start.

I’d avoid any add-ons. We had a discussion a few years ago about a Ford diesel owner who fried his engine with an add-on ‘tuner’. Ford said ‘tough’, as did the tuner maker…VERY expensive…

Also, make sure your tires are at least AT&T he Dodge recommended inflation pressure. I usually put 3 to 4 psi over the recommended level so that it deflates over time to the recommended level. Then I refill. And check tire pressure once a week or every other week.

Thank you all for your input, really appreciate it.

The only real reason(economic wise to get one of these diesels) is the pulling power,the mileage on these things is good(relatively speaking) not great ,any serious gas V-8 now will get that mileage with ease in your case the extra weight is gonna knock the mileage pure and simple and if(Heaven forbid) you have to repair that thing,you are going to pay a heavy duty price.A couple of things you can do to help mileage is to make sure the clutch fan is working and if you are really serious about better mileage step up the final drive ratio to put the cruising speed into the engines sweet spot(it will pull it,all that torque)

The diesel motor becomes comparably economical while under load. The best way to realize it’s economical benefits over a gas motor in a HD truck is to tow or carry heavy loads. That 16 mpg will look much better when it drops less then a gas motor working hard. If you are using any heavy duty truck for commuting, gas or diesel, you will be disappointed.

I remember very well that discussion about the Ford diesel owner that texases mentioned. A brand new top of the line truck that made it from CA to Flagstaff, AZ before the engine went belly-up due to a Banks kit being installed on it.

Twelve grand of no warranty later… :frowning:

Last I checked a lp addition was about 3 grand last I checked http://www.americandieselsystems.com/index.php