mpg's?

I talked to someone with an 04 recently that is screaming, 4.8-5.2 mpg. I asked someone with more knowledge about the 14L Detroit than I have and he told me this is common for them at the 515 Hp with the EGR

 

I have an '04 Classic XL, 14l 10 speed auto shift with 3.55s. I have gotten 5.8 mpg regularly since buying the truck in '08. I recently got a new turbo and had the egr system gone through and my first shot at checking my mileage was today. At 80,000lbs from Indianapolis to Aberdeen MD then Front Royal to Richmond I got 6.77 mpg.
I sure hope I can regularly see 6.7 now.

 

I used to drive a former Trans Am 04 Columbia with the 515HP Detroit, 3:58 rears, 22.5 tires with the smart shift. The best I got was 7.17mpg with 25K of flowers. Also with a full load, I got 5.8mpg. If my former boss did not go to California and was able to disconnect the EGR, I am sure we would see better than what I am posting.

KH

 

Depends more on what truck its in than the transmission.

2006 Columbia Condo (2005 Series 60 - 515 bhp, should be same spec as 2006)
Chrome Hendrickson Bumper (Hurts Aero)
No Tank Fairings
13 Speed RTLO (0.73)
3.58 Axles
24.5LP
1400 rpm at 65 mph.
Average Load 35,000 lb
Run southeastern states
Average MPG for last 40,000 miles - 7.4 mpg (65 mph)
I loose roughly 0.6 and 1.2 mpg at 70 mph and 75 mph respectively and gain 0.4 mpg at 60 mph. Gains at 55 mph are minimal over 60 mph as 12th does as well as 13th. Truck isnt really geared optimally for 55 mph.

PS Make sure the overhead is done correctly the specs are different than the pre-EGR 12.7L. And can effect both power and economy.

 

2010 Freightliner Cascadia
DD15 power plant
8 speed

I average 7.5 to 8.1 deppending on the terrain and whether or not I use progressive shifting.