I now have 20K on my '07 LMM. My truck has 33" tires and a 4" lift, I'm sure that hurts mpg a bunch. I'm also running a Bullydog programmer at the medium (tow / econ) setting. Unloaded freeway driving I'm averaging 19 mpg and in town driving about 13. Loaded with trailer (about 12000 lbs plus truck), it drops down to under 14 on the hwy. I have found that the speedo correction from Bullydog does not work. I called them, but received the 'we haven't heard of that from anyone else so there's nothing were going to do about it' response. But, the speedo is off by about 3 mph, which would affect the mpg upward a bit, but I'm not a good enough mathametition (sp?) to figure it out. So the mileage is improving as the truck gets more miles on it. I would also agree that 55 - 60 is the sweet spot, at 70 I drop by about 2 mpg. Adversely, my '03 duramax improved it's mpg as the speed increased...