I would like to know what kind of gas mileage people are getting with the new six-speed automatics. Is it 1-2 mpg better than the four-speeds, or no different. The vehicles at the dealerships do not have gas mileage numbers on the window stickers. Of course the sales person will say mileage is better, but what really are the results from owners?

 

My tuned AWD 6.2 is knocking down 19-17mpg on average in the summer. Winter is a different story; 14-15mpg then. Thats probably a solid 75%+ highway though. My highest was 23mpg. I got that 1 time so I think it was a fluke more than anything. My trip from Minneapolis, Minnesota to Joilet, Illinios last summer gave an average of 18.2mpg IIRC.

 

Kewl. A good tune does make a difference. I adjusted mine (5.3 4-speed auto) to the point I get 17-18 mpg around town, but highway mileage above 20 mpg is still elusive.

It is good to know your AWD 6.2 is getting such good mileage. That's a 6-speed automatic? Like yours, my winter mileage drops.

 

my o9 sierra 5.3 gets pretty good on the hwy but it also has AFM... seems bout the same as my 06 5.3 4l60e... but the 06 did have 323 rear where as my 09 6l80e has a 342 rear FWIW... bout 15-17 in town and bout 19-20 hwy

 

That's about what my 06 CC/SB Silverado Z71 got out of the box. I'd average 17 in my 32 mi each way commute into Tampa, If I was on the highway I could squeek out 20 to 21 MPG below 70 MPH. At 80 I got about 17 to 18. I do notice on these trucks the A/C makes a difference in fuel economy. On my ford it was the same, on or off. Don't know what the difference is. I figured a/c is a/c.

 

My 2008 Sierra Denali AWD with intake and a replacement muffler gets anywhere between 18-22 mpg on the highway averaging between 65-75 and about 12-13 in the city. I drive pretty hard in the city though.

 

yeah im shooting a lil low on mine right now... im only on my 3rd tank of gas... lol... i dont drive her to work... and of course the 1st tank came from the dealer and didnt have all the milage things reset... im sure it will do better... the dealer i bought it from is bout 100 mi. from my house... and on the way back i did see 23mpg in V8 mode @ bout 60 -65.. when i put her up to 80 it was bout 19 on the instant milage setting.. ill have to have to manually...lol... on my next tank.

 

Not too shabby. Are you 2wd or 4wd? I notice the 2wd units get at least 2 mpg better, must be the 400 or so lbs, higher stance (more wind going under the truck and CVs spinning).

 

2wd....