[GMMediumDutyMQ]

Does anybody out there have some "real world" fuel economy results for the new Tahoe 4X4 with DOD? I am planning to purchase a 07 Silverado when they come out and am curious as to how much better fuel mileage they will actually get compared to my 2001 Sierra 4X4 (17mpg on the freeway at 75 mph)

It's not all that much better.

Our '07 2LT 4x4 doesn't get much better than 14.6 average fuel economy. Which, in comparison to the '06 Escalade EXT we had previously, isn't really much of an improvement - considering that truck also had the 6 liter...

The main problem is pretty evident: calibration. If you have a chance to drive a 900 with this system, look at the information display that shows instant economy; it also shows what engine mode you're in.

The problem lies within the fact that any touch of the throttle - no matter how light - instantly throws the engine back into 8 cylinder mode. The only times I really see it run on 4 are when I'm coasting.

As a result, times where 4 cylinder mode could be advantageous - light throttle, low-speed launches, etc. - are bypassed, and subsequently, so are the fuel savings.