6.6 Gas MPG

Skidaho · November 23, 2019

2020 Denali 6.6L w/20” stock tires w/2500 miles averaging around 10.7-11.5 MPG per fill up mostly short trips around town and minimal highway.
Averaging around 16 on the interstate @ 70 and got over 18MPG during break-in period @ 50 MPH.

Getting around 11 MPG on the interstate with a quad in the back (850#) driving @ 70.

Towing 7500# travel trailer getting around 8.3 MPG average @ 65 MPH.

Getting only around 10 MPG while hunting at low speed 5-10 MPH or less in 4-wheel drive on snow trails. I expected a little better economy with the low speeds.
Overall I love the truck and will just have to live with poor fuel economy.

Cowpie · November 23, 2019

TN05, give it a try for a while staying out of 6th and see what the results are. On the rural, rolling hill highways in my area, I typically run in manual mode 5th, keeping it out of the top OD. Keeps the RPM's around 21-2200 at 60 mph with my 6.0 / 4.10. When using regular fuel in that scenario, I would typically get an average of 14 mpg for all miles (in town, rural highway, gravel roads, hauling, etc). I only let it go into 6th when I will be out on the interstate and going 65 or more. 17-18 mpg on road trips. But I have 4.10 and 33.2 tires. You have 3.73 and 34.5 tires. You will just have to play with things and see what works best. But I will be willing to bet you should see an improvement in mpg if you keep the RPM's a little higher in most situations.

Cliff

Edited November 23, 2019 by Cowpie

SierraHD17 · November 23, 2019

Yup. Let it Rev a little bit. It's something people never understand when i talk about my 2017 and the gear swap. I only run a 295/60/20 which is close to these 2020 trucks stock tires With 4.56 I am about 2150 rpm at 70 mph and it does fine. Before I did the gears I was turning under 1800 rpm with 3.73's and the truck did not like it. I know people will run out in droves and tell me a 6 liter doesn't matter but it does.. the 6.6 has more power but it's not magic. Until I swapped gears for highway driving I ran my truck in fifth and never used 6th gear.. the mileage actually improved marginally and the truck just drove better. Of course now 6th is fine but I have the rear axle ratio to compliment it.

wowens79 · November 24, 2019

22 hours ago, Skidaho said:

2020 Denali 6.6L w/20” stock tires w/2500 miles averaging around 10.7-11.5 MPG per fill up mostly short trips around town and minimal highway.
Averaging around 16 on the interstate @ 70 and got over 18MPG during break-in period @ 50 MPH.

Getting around 11 MPG on the interstate with a quad in the back (850#) driving @ 70.

Towing 7500# travel trailer getting around 8.3 MPG average @ 65 MPH.

Getting only around 10 MPG while hunting at low speed 5-10 MPH or less in 4-wheel drive on snow trails. I expected a little better economy with the low speeds.
Overall I love the truck and will just have to live with poor fuel economy.

What gear and RPM does it turn at 65 with the TT? My old 6.0 with the 4spd won't hold 4th, so I have to drop to 3rd and turn almost 3000rpms on the flats.

Are you pleased with the way it handles the TT?

Skidaho · November 24, 2019

Handles the trailer really well. Would have no problem going faster but want to keep things safe. Sure beats the 2008 Silverado 1500 with 5.3L.
I don’t recall the gear and RPM. Will report back on that in the spring.

wowens79 · November 24, 2019

7 hours ago, Skidaho said:

Handles the trailer really well. Would have no problem going faster but want to keep things safe. Sure beats the 2008 Silverado 1500 with 5.3L.
I don’t recall the gear and RPM. Will report back on that in the spring.

Thanks!! I'd imagine you are done camping for a while.

captinmrgan · November 24, 2019

Brought my double-cab home from the dealer yesterday. 85 mile trip, mostly highway, maybe 10 min of stop and go traffic. 18.0 MPG average when I pulled in my driveway.

Ray Pickle · November 25, 2019

Just drove home a crew cab 2500 lt and got 18.3 over 90 miles . 80 of ot was hwy. with cruise set to 71 mph. Did the same on lease return 2016 2500 crew cab "47000" miles, and got 15.3 going to dealer.

texasnavy05 · November 25, 2019

On 11/24/2019 at 1:24 PM, captinmrgan said:

Brought my double-cab home from the dealer yesterday. 85 mile trip, mostly highway, maybe 10 min of stop and go traffic. 18.0 MPG average when I pulled in my driveway.

1 hour ago, Ray Pickle said:

Just drove home a crew cab 2500 lt and got 18.3 over 90 miles . 80 of ot was hwy. with cruise set to 71 mph. Did the same on lease return 2016 2500 crew cab "47000" miles, and got 15.3 going to dealer.

On 11/24/2019 at 1:24 PM, captinmrgan said:

Brought my double-cab home from the dealer yesterday. 85 mile trip, mostly highway, maybe 10 min of stop and go traffic. 18.0 MPG average when I pulled in my driveway.

I'm assuming these are from the DIC readouts? What are your distance current and best mpg's? I'm just trying to get an apples to apples to see if my slightly bigger tires are having that big of an impact.

My 25 mile current is 13.4, best is 17.2

My 50 mile current is 12.8, best is 14.8

My 400 mile current is 12.1, best is 12.8

Also, I'd be interested in your hand calculated mpg once you get through a few tanks. My DIC is typically off by 0.5-1mpg

MTU Alum · November 25, 2019

6 minutes ago, texasnavy05 said:

I'm assuming these are from the DIC readouts? What are your distance current and best mpg's? I'm just trying to get an apples to apples to see if my slightly bigger tires are having that big of an impact.

My 25 mile current is 13.4, best is 17.2

My 50 mile current is 12.8, best is 14.8

My 400 mile current is 12.1, best is 12.8

Also, I'd be interested in your hand calculated mpg once you get through a few tanks. My DIC is typically off by 0.5-1mpg

Are you correcting for your miles driven based on your odometer not being correct? You are driving more distance per rev than the vehicle thinks you are.

Ray Pickle · November 25, 2019

Just drove home a crew cab 2500 lt and got 18.3 over 90 miles . 80 of ot was hwy. with cruise set to 71 mph. Did the same on lease return 2016 2500 crew cab "47000" miles, and got 15.3 going to dealer.

Ray Pickle · November 25, 2019

I agree with the other posters comments. Secondly sa you are probably aware, your effective gear ratio is lower numerically which could move rpm below optimal efficiency for max. Mpg at hwy. speed. My mileage was via DIC I have literally owned the truck for 3 hours.

captinmrgan · November 25, 2019

18 minutes ago, texasnavy05 said:

I'm assuming these are from the DIC readouts? What are your distance current and best mpg's? I'm just trying to get an apples to apples to see if my slightly bigger tires are having that big of an impact.

My 25 mile current is 13.4, best is 17.2

My 50 mile current is 12.8, best is 14.8

My 400 mile current is 12.1, best is 12.8

Also, I'd be interested in your hand calculated mpg once you get through a few tanks. My DIC is typically off by 0.5-1mpg

Yes, it was from the DIC readout. I haven't even gone through my first tank of gas yet. I will check DIC versus actual mileage and re-post. I have a road-trip planned this week so I should get some good data.

texasnavy05 · November 25, 2019

12 minutes ago, MTU Alum said:

Are you correcting for your miles driven based on your odometer not being correct? You are driving more distance per rev than the vehicle thinks you are.

Good point. No, I havent been correcting for the difference in circumference. the difference between stock tires and mine is about 1.6" in circumference (1.5%) so I could adjust all of my mpg by 1.5%

12.9 mpg would go to 13.1

12.1 would be 12.3

11.9 would be 12.1

ShotgunZ71 · November 25, 2019

Here's my "bests" after 4100 miles:

18.9 over 25 miles

18.0 over 50 miles

16.3 over 400 miles

Overall with all driving and towing the TT, and now 5th wheel, my overall is 12.2 mpg for all the miles. My DD is a 2 mile trip to work and a 2 mile trip make home. I also one who warms up a vehicle in the colder mornings.