6.7L Cummins Forum

Is there anything that can be done to get better fuel milage on my 6.7?
my old 5.9 got almost 22 mpg on the road not pulling trailer, my 6.7 only gets a

round 12 to 14 mpg. any suggestions?

Hello Jerry,

Welcome aboard !

What axle ratio do you have ? Can you provide some details ? Do you have a 4x4 ? What did you have before ?

One thing you to remember is that the 6.7 has a smog system that requires periodic regen that consume fuel (up to 4 liters per regen). The smog system is also somewhat restrictive so we loose some more mileage.

There are things that can be done but some info about what you have will help us help you.

Cheers.

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Same issue. 2008 -6.7, SRW, 4X4, 4.10 gear, Mega Laramie. Love the truck, but this thing is a gas hog. I'm currently getting aroung 13 as well. Have considered changing the gears since I can do this myself plus the cost of parts. Any advice appreciated.

Excuse my error---diesel hog!

my 2011 6.7 get 13 to 14.5 around town and 18 on the road driving 70 to 75. I think it has 3.73 and is a 4x4 crew cab. I would like to get over 20mpg but don't want to void warrenty.

my 08' 3500 4x4 is getting 15-16 in town and 75 mph on highway getting 22 on average. Had 5,000 pound gooseneck trailer with 16,000 pounds of cattle in it. Was 2 and half hour drive at 98 degrees out and was still getting 13 mpg. Only issue was the flat tire on the trailer halfway home. That was an interesting tire change. Truck is stock to

The best thing you can do is delete the dpf and egr and get a tuner that will correct the error codes.

Or you can buy an H&S tuner and you dont even have to remove the dpf and egr you just deactivate them.

I have both deletes and the h&s blackmaxx on my 08 3.73 gears. i get 22-24 highway and 13-18 towing depending on the load.

regarding the warranty issue you might have to deal with poor mileage. but honestly if you get rid of the smog you will probably have less problems and may not even need the engine warrenty.

Bottom line, it all depends on how much money you want to spend to achieve mileage and understand that you will not break even in any way shape or form. These trucks are heavy, 6.7L engine, and drive train designed to move a house. Not all states can you do a delete and pass smog checks, some states any smoke (no matter how much) from the tail pipe and you fail. Also you can not compare a 5.9L to a 6.7L and expect the same mileage.

On my truck with all the mods done, I broke 20 MPG (on a dually with 2 adults, 2 kids, 2 125 dogs, full tank, 400 lbs 5th wheel, 1050 lbs misc weight, no trailer, 68 MPH average) and smog system completely functional on the highway by hand calculation (not using the overhead lie-o-meter).

Things you can do it change down to a 3.73 axle ratio, manual locking front hub assembly, real cold air intake (sucks cold air from the front of the truck), ats co-pilot tranny controller (this helped me break 20 MPG), using synthetic gear oil, mandrel bent dpf back tail pipe exhaust (too many sharp bends on a our stock tail pipe). Other things you can do also is air up your tires to help reduce rolling resistance. Going to 19.5 with stiff sidewalls helped my mileage on the highway alot, did nothing for the city usage, but my needs where for highway. Another thing that helped me was diesel additive to raise the centane levels and reduce the number of regens (moving towards trying a new type soon, cummins additive too expensive).

Hope that helps, if you have more questions, lets chat about it and see what other info we all can come up with.

Cheers.

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I sort of agree with all the above. Modifications rarely pay for themselves, deleting EGR & DPF they say helps but you run the risk of detection. However, listed below are suggestions that will help, are at additional no cost and are not illegal:
1. Slow down, on level interstate hold steady speed, get in the right lane & relax
2. Increase your following distance, touching your brakes hurts your milage, ever ride with a tailgater? Gas - brake - gas - brake this = major fuel consumption
3. Air up the tires, don't wear out the centers but it is a truck and will ride stiff
4. If you can, use your foot for a cruse control, hold peddle the same, it will increase speed going down hill but it will slow down going up hills, don't impede traffic or get a ticket but use this for your benefit (increasing speed going up hill = major fuel consumption)
5. Beating another brand to the next stoplight is cool but costs you money (your choice)
6. Diesels like heat, I cover my grill and watch the temp (you will be surprised)
7. Walk to neighbors house, those 1/4 mile short trips are killers (gas & diesel)
8. Use good oil & keep it clean, I use AMSOIL but to each their own
Yep, call me a Cave Man but, 100 pennies = 1 dollar - etc. My family can not spend more money than we take in, private individuals can not do this for long if they plan to own their own home and be successful. Happy motoring

ssiple, great advice ! I especially like #1. Can not call you a cave man, one myself, also pickup all pennies I find

In my case at 1000 miles a week, will it pay for itself ... somewhat. The mountain passes are the ones that burns the fuel.

Can you elaborate more on the #6.

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