GM's estimate for the 1500 equipped with the new Vortec 6.0 liter and four speed transmission is 15/19. There are no estimates listed for the 2500HD with the six speed transmission. GM boast that the six speed will increase gas mileage, but the only way to purchase a six speed at this time is to buy the 2500HD. The extended cab 2500HD weighs approximately 900 lbs more than the 1500 extended cab. Was wondering what kind of mileage to expect from the HD. Anyone driving a HD2500 yet?

I had a 2001 2500HD with the 6.0 and while I loved the truck and the way the engine ran, it was a complete pig on fuel. I got better mileage from my '90 3500 with a TBI 454.

My current 2500HD (2005) is a Duramax/Allison equipped beast and I won't be going back to gas engines in anything beyond a 1500.

I suspect that the Allison would help the 6.0 do better than my old '01 did, but I don't imagine it would help enough.

My Max has a 6.0L, chassis weight is down compared to the HD but the engine is still a fuel slut. My avg. is 16.5 MPG and that is with light foot.

16.5 MPG?

I would have been overjoyed to get that in my '01. I was lucky to get 10-11 MPG downhill with a tailwind!

GM's estimate for the 1500 equipped with the new Vortec 6.0 liter and four speed transmission is 15/19. There are no estimates listed for the 2500HD with the six speed transmission. GM boast that the six speed will increase gas mileage, but the only way to purchase a six speed at this time is to buy the 2500HD. The extended cab 2500HD weighs approximately 900 lbs more than the 1500 extended cab. Was wondering what kind of mileage to expect from the HD. Anyone driving a HD2500 yet?

you can't compare the 1500 to the 2500hd... for one they are different chassis and different trannys... also they are different engines... while the 6.0 vortecMax is a similar the the ls2 where as the hd motor is iron and designed completely different... the 6.0 and 8.1 are designed more closely to the ls1...

although the bore and stroke has been changed from the car motor... also the heads and intake runners are different...

the vortecmax and the hd 6.0 are not similar at all...

My Max has a 6.0L, chassis weight is down compared to the HD but the engine is still a fuel slut. My avg. is 16.5 MPG and that is with light foot.

I've never gotten more the 16 mpg on a tank with my Suburban (with a 5.3) even with driving entirely on interstate with the cruise set the entire time. So, I wouldn't gripe about 16.5mpg.

Well im not really complaining about 16.5, i'd drive a Aveo if i was really concerned about. . .

Well im not really complaining about 16.5, i'd drive a Aveo if i was really concerned about. . .

I didn't mean for that to sound like that. I didn't figure you were too concerned as you opted for the 6.0 in your pickup vs. the 5.3. I'm not that concerned either otherwise I wouldn't own a Suburban, just saying that 16.5 would be nice.

I drove a lon g wheelbase 2500 Chevy van with the 6.0 liter and I didnt think it was so bad. I figured about 16-17 mpg for what we did with it which we thought was very good for the huge size of it and the power it had. I thought it had a really good amount of power.

The 6spd. auto in a 2500HD and the 6.0L would be about the same as the 1500 with the 6.0L and 4spd. auto maybe even better.