Krash,
I have both, here's the scoop.....
Don't let anyone tell you they're getting more than 10 -11 MPG on the 8.1. Our Yukon XL get 8 -10, and spends more time getting 8 than 10 (city and highway mix)
The oil consumption on the 8.1 is a major bummer...... I have to add a quart at every 3,000 miles
I will solve this problem as soon as GM comes out with a 2500 yukon XL with the D-max
The D-max, well since I broke 50,000 miles, 19-20 (city and highway). Before 50,000 the best I could get was 16 to 17 but often got 15 MPG
If MPG is your goal, the D-max beats the 8.1 in the long run..... hands down.
Edited by: Blinky