I have a 07.5 6.7L with about 7600 miles on it. When I first purchased it, I was getting around 17-18mpg. Now I am only getting around 15-16mpg. Is this a sign of a problem, or can this be normal?

 

Depends on what else has changed. Be sure and check your air pressure in your tires. Are you running with the AC turned on now versus before? Are you using the same fuel as before? Have the refiners switched from Summer blend fuel to Winter blend? Any of these things could make the type of change you are seeing.

Assuming the truck still runs & feels the same, for such a minor variance I would say it's nothing to worry about unless it gets worse.

 

The truck still runs and feels the same, thanks for your advice MtnTrucker.

 

Your info says your from Nevada but what part. Are you in an area that has already started using the Winter Blend ULSD? If the you are that could be the issue.

 

I wish mine was ever that good. I get between 12 and 13 so far around town, not much highway and a lot of short runs and start/stops. Not the best thing for a diesel. The overhead picks up to 15 and 16 when I get on the freeway at 75 MPH. No loads pulled so far, only 700 miles on the OD. No problems yet either.

 

When was your rig purchased? Does it have the latest flash (AU)? One of the primary focuses of the more recent TSB's has been to get the DPF's in these units to regenerate more frequently, thereby not allowing them to clog up. More frequent regeneration events (including active events where diesel is added to the exhaust stream to increase EGT's to aid in the process) causes more fuel to be used. If you took delivery before mid-June, this could be a likely reason for your decrease in fuel mileage.

 

If you're speaking to me, I took delivery 8/30 and the truck was built in June. I can understand the AU and the gas mileage thing so I image that my truck has this then...

 

Let the Cummins get some miles on it (like 25000-30000) and your MPG will go up. BTW 13 MPG in town isn't to bad for a new truck. My 2006 was getting that on the highway at 65MPH for 60 miles until I got 25000 miles on it, now I'm getting 18-18.7 (3500 auto).

 

Thanks, that is what I've heard and would hope for in the miles to come.

 

I don't think so on this engine. That happened on my 04. I have 17500 miles on mine and avg. Total about 14.2. All types of driving.

 

If our milage ever does improve then mine'll probably be out of warantee and fallen apart possible with the low miles I put on my vehicle. Long time to wait for break in and improvement if it ever does come.

 

Yeah, I'm lucky if I get 14.5 Hwy hand calculated.

 

heres the whole problem.

Gas Mileage Inconsistent

you're putting gas in, you should be running diesel