New GM 2500 6.0/6 spd combo

asylum575 · Jan 29, 2008

Anyone have a 2007/2008 CHevrolet Silverado/GMC Sierra 2500/3500 series with the 6.0 Gasser and new 6 spd tranny. What kind of MPG are you getting. I have an 2006 with the 6.0 and 4 spd. Love the power, but what a pig on gas. Getting 10-12MPG empty with a 2WD. I like the new body and would like 4WD, just wondering about the MPG. I could get by with the 5.3 with the AMF. Don't really pull anything more than a tandem 7000 trailer.

rutwad · Jan 29, 2008

I did not think the 6 speed was available with the 6.0. Well, maybe the new ones are. I still would not expect much more than you are getting with your truck now.

Builder · Jan 29, 2008

My HVAC sub has 2 or 3 of the 6L GM gassers and they suck gas down pretty bad.

Kahuna · Jan 29, 2008

I was getting that same 10-12 mpg with a Ford F250 5.4 gas, but at least you have the power. I don't have that truck any more. When I bought the Ford I was looking at the Chevy 6 liter. The Chevy dealer told me it was a hog and not to expect anything more than 12 mpg.

Z-Michigan · Jan 29, 2008

rutwad said:
I did not think the 6 speed was available with the 6.0. Well, maybe the new ones are. I still would not expect much more than you are getting with your truck now.

It's not the Allison 6-speed used with the Duramax, it's a different GM 6-speed that was introduced in the Escalade, then Yukon Denali, and now in the heavy-duty pickups with the 6.0L gasser. Still a very good transmission (and the Allison would be double what the gasser needs). Can't comment on the mpg of the 6L/6-speed combo, but I wish I had the 6-speed in my 5.3L Suburban!

KAB · Jan 29, 2008

I have heard that with the 3.73 axle ratio there is an improvement. The guy was filing up less often. I did not find out how much further per tank.

Kurt

TX48 · Jan 29, 2008

I just bought an 07 new body ext. cab 2500 HD,in Dec. with a 373 rear end. From day1 I have gotten 15 mpg, mainly highway. Pulling a 2horse trailer with the trailer tow on I drop to 9.5. This is a fast truck with 360 hp. I run about 70 (give or take). I was told if I had the 410 rear my mpg would be awful. I was a ford guy ( and still like Ford) but the 5.4 is gutless compared to the 6.0. I decided that the duramax was to much and couldnt justify buying it. Later John

Builder · Jan 30, 2008

TX48 said:
I just bought an 07 new body ext. cab 2500 HD,in Dec. with a 373 rear end. From day1 I have gotten 15 mpg, mainly highway. Pulling a 2horse trailer with the trailer tow on I drop to 9.5. This is a fast truck with 360 hp. I run about 70 (give or take). I was told if I had the 410 rear my mpg would be awful. I was a ford guy ( and still like Ford) but the 5.4 is gutless compared to the 6.0. I decided that the duramax was to much and couldnt justify buying it. Later John

Man, they're up to 360HP? That's pretty impressive for a 6L gas truck engine!

rutwad · Jan 30, 2008

The 315 HP 5.3L has Active Fuel Management (or similiar), where it runs on 4 cylinders until more power is needed. Is this available with the 6.0L?

I wasn't sure about the 6 speed because I was thinking about 1/2 ton trucks.
The only way to get a 6 sp. there is to get the Denali with the 6.2L. I have heard the transmission should be available for all 1500's in 2009. I guess it is already available in HD trucks.

Earlier models required either the Duramax or 8.1L to get the Allison. Since GM did away with the 8.1L, is the Allison only available with the Duramax now?

john_bud · Jan 30, 2008

asylum575 said:
Anyone have a 2007/2008 CHevrolet Silverado/GMC Sierra 2500/3500 series with the 6.0 Gasser and new 6 spd tranny. What kind of MPG are you getting. I have an 2006 with the 6.0 and 4 spd. Love the power, but what a pig on gas. Getting 10-12MPG empty with a 2WD. I like the new body and would like 4WD, just wondering about the MPG. I could get by with the 5.3 with the AMF. Don't really pull anything more than a tandem 7000 trailer.

If all you pull is a 7k trailer, get the 1500. I had a year 2000 1500 4x4 5.3L auto ext cab short bed Z71 and it pulled 9k pretty well, but it was marginal on control. But pulling 7k would be fine.

That truck got 16.08 mpg lifetime (by hand). Of that about 1/4 was pulling 9k. Best empty was 20.6 at 65 mph on a 70F sunny day. Worst was 8.6 pulling 9k into a strong headwind in the cold. Mostly towing was about 10-11 and mostly empty was about 17 mpg (47 of 113 tanks were 17 or more).

jb