Just got a new 05 CCSB and I cant believe the MPG! I drove from Atlanta to Clevland Tn. and averaged 19.4! My 03 was lucky to get 16.

Is this what you are reading off of the computer or did you calculate by hand? How fast were you driving on average?

By Hand...21.8 Gallons replaced w/422 on the ticker. Drove up I75 at about 75mph and took the senic route home through the mountains. Dic showed 19.6.

scenic

Is the computer (DIC) not very accurate?

On 35-40 mile trips my 05 will get 17.x even with me passing every now and then under full boost… 

I only get 15.9 -16.5 in the city though.

The dic seems to be close untion you put on a power chip. My 03 would show higher numbers than actual.

20.5 mpg city / highway for mine. but only get 19.0 on th highway with the cruize set at 78. Just got a new 05 CCSB and I cant believe the MPG! I drove from Atlanta to Clevland Tn. and averaged 19.4! My 03 was lucky to get 16.

check it by hand to make sure your, that way you can see if your DIC is off or not.

I went to utah two weekends ago (unloaded). About 300 miles each way. I set the cruise at 80 and got 13 mpg. Does this seem unusually low? BTW don't think I have any injector problems- no white/blue smoke, never lacks for power.

Do they get better mileage after a few thousand miles is on it.

Yes. The engine takes between 5k and 20k miles to completely break in. You will typically see better and better fuel mileage as your engine breaks in. From the cummins diesel website concerning break-in of a cummins diesel :

"How many miles does the Cummins engine require for break-in?
In general, 5000 miles. This depends on the type of driving the truck is subject to; hauling or towing a load will shorten the break-in period. Light duty hauling or "babying" the engine can delay full engine break-in for up-to 20,000 miles."

2. Oversize tires will kill fuel mileage.
3. Speeds over 70mph and fuel mileage drops like a rock...

jeff

Brand new 05 cc 2500 also. So far in town and rural road driving is all I have done and I am getting 19.

Another thing to note is that the engine is not efficient until it is completely warmed up. As a result, short trips can yield very, very poor fuel mileage. So one man's city mileage can differ greatly from another...

Reset the average fuel mileage on the DIC right when you start up the truck on a cold morning and you will see what I mean...

jeff

I went to utah two weekends ago (unloaded). About 300 miles each way. I set the cruise at 80 and got 13 mpg. Does this seem unusually low? BTW don't think I have any injector problems- no white/blue smoke, never lacks for power.

13 mpg seems low, even for 80mph. Do you have the 4.10 rear end?

I didn't know that gm even offered a 4:10 rear end.

I've got the 3.73 rear end. Btw, that 13 mpg was with edge on 1.

my 04 lly gets about 15-16 around town. at 75 on the hiyway about 15 empty 8-10 with 5000lb trailer load, 8-9 with big trailer. was getting 22-23 when it was new. have about 24000 on it now. the milage gets worse the more miles i put on it.

my old 6.5 got 4-5 mpg better when i stepped up to the 285's so i'm thinking i'll try that. btw mine is tottlay stock.

I didn't know that gm even offered a 4:10 rear end.

3.73 ONLY in '05. I'd guess the same for '04, eh?

I am getting 8.8 mpg under tow (16,000 +). I have not done enough driving without the 5th to get a good mpg yet. But I did started out with 7 mpg in Kali. Then I decided to hauled my 5th to Alaska now I get around 8.8.


Tony