Quote Originally Posted by gimpyhauler View Post
Sure would like to hear more about that tune. That is an impressive mileage gain for cruising.
This was with an EFILIVE tune that I got from another forum. I tweakd it slightly to smooth it out, but it is a pretty basic tune. About 2-4 degrees more timing in the cruise area, and the boost was lowered about 3-4 pounds at cruise as well as opened up the turbo vanes. It made it a little sluggish to respond to throttle changes, but it was a good trade-off for the milage gains. Plus it was a DSP5 tune so all he had to do was flip the switch on the dash and it came right back to life.

Quote Originally Posted by Mark Rinker View Post
My observations are have been that LBZ and LMM powered trucks get about 15% -20% less MPG than the LB7s when driven unloaded.

When towing, the LMMs do a little better than the LBZs, and only about 5% - 10% less than their LB7 predecessors, with much more stock power and a much greater ability to diffuse heat from the cooling stack. The LMM is a major improvement over the LB7 in the power department for just a little more fuel consumption, and still a measureable improvement over the LBZ family in both MPG and heat management.

After 11 years of production, team Duramax continues to improve...
With a basic tune the LBZ and LMM can both get almost teh same milage as the LB7's, and like you pointed out they are so much more refined and powerful. After tuning and driving one, I kick myself for swapping in a LB7 into my BURB, the LBZ would have been worth the extra effort in the end.