I've read many posts about how mpg increases with more miles. My experience with gas engines is they get the best mpg when new and it doesn't get better with age. This is my first diesel so I could only go by what others told me about what to expect for mpg. The first 12k miles on the truck I would get 15-16 mpg driving to work and around town. Pretty good for a truck of this size and power. I took a few trips (100-200 miles) and the best was 17.5 mpg. Wasn't real impressed but not complaining. Well a few weeks ago we took a 1200 mile round trip from IN to PA pulling a 24' enclosed trailer with my GTX inside. Best mileage was 12 (flat roads, no head wind 65-70 mph). Not impressed but not complaining. The following week we drove the truck on a 200 mile round trip (no trailer) and I got 19.5 mpg! Now that's what I'm talkin about! Not only did the mpg go up but the engine seems quieter now. Now I'm starting to believe!

 

These Cummins just love to be worked. Drive'em hard pulling heavy and they just keep on purring. Reminds me of the older Datsun 280z straight six that I love so much and still have one, turbo charged of coarse.

 

yep was getting 15mpg avg at 20k mi now 20mpg avg at 46k.

 

267,xxx miles average 18.6 in town.. hand calcualted. and 22.3 on the road trips we take. lovin it...

 

After 55000 miles my truck's running better than ever. Better mileage, more power. I read about these engines getting better with time, but I didn't realize how big a difference it would be.

 

I can also attest that the mileage increases with time and work. If you see your mileage dropping off and changing the fuel filter does not bring it up, go haul a really heavy load and work the engine harder. My last 3K trip hauling my 5er brought mine up. Guess it was time to work some.

CD

 

I now have 20,000 miles on mine and mileage has gone up to average 18 mpg.

 

I am up to 70k and averaging around 500 miles per tank, which averages out to around 18mpg. Much better than 15mpg at 40k.

 

Mine runs excellent after a good heavy towing workout. It starts to rattle and vibrate after just being a grocery getter for awhile. Hook up about 10,000 and after that she purrs away and the mileage jumps up. The harder you work 'em the harder they work. Sure seems backwards but you gotta love it.

 

I'm starting to get impressed with my mileage. The last 2 fill-ups I hand calculated 18.5 and 18.7 for highway driving. With in-town/highway I'm getting 16.5 on the last tank I calculated. I only have 6,600 miles on my 2007 5.9 4-speed auto.