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Just got my 2020 2500hd 6.6 gas LTZ 2 days ago and I’m impressed across the board. The mpg is a great improvement in my opinion. I have a 2009 duramax on 35’s , 2007.5 6.0 4:10 on 35’s and a 2018 6.0 4:10 service body with the stock 265 tires The best ever on the duramax Highway when it had 265 was 16.6 on the 35’s its around 14 and once got 16. Towing my center console it’s 9.5-10 and my TT its 8.5-9.5 depending on flat or mountains. My 07 gets 12.5 average and around 7 with TT 8.2 with boat . The 2018 averages 14.5 and straight highway has got 17.1 once . Never towed the boat or TT with it . This new 6.6 running 70 got 17.2 highway . Running 63 on cruise for about 100 miles got 18.3. After the first tank with pure mixed driving including towing the boat 50 miles , sitting at idle for 40 minutes, 4 drive thrus , highway and backroads it’s still at 15.3 . Seems awesome to me I have the 20 inch wheels and the tires are only about a 1/4 inch shorter than my 35’s measuring them on the truck. Not enough to visually tell. Pulling the boat at 68 mph I was getting 9.3 mpg. The power is noticeably better especially when I got back in my 2007. It really felt slow afterwards.Towing the boat it seems faster than my 2007 . Is everyone else feeling this way ?

Edited by Carolina
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I am halfway thru my trip from cincinnati to big pine key florida, first tank in driving rain 8 mpg, 2nd tank 8.9 3rd tank 9.1 4th tank 9.3. I will be returning home in a week and will update. I am to

I just finished a 600 mile round trip from Sc thru NC and TN mountains towing 9130 pounds . Interstate grades were a 3 mile 6% , 1 mile 7 % ,  6 mile 7% and a few 10% backroad grades . I can say I was

Hi everyone I’m a newcomer here decided to join as I just bought a 2020 Chevy 2500 lt z71, ccsb with the l8t. We love the truck more than we thought we would, huge improvement over the 6.0, which IMO

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2020 HD LT Crew Cab, 4x4. 4k miles, 4 months old. 6.6 gas, 20" wheels. Very stable platform for me when pulling my 33' RV, 7k empty. Gas mileage 12-15 average, 7-9 when towing. Mostly country roads. I didn't purchase this 7k lbs truck for the mileage so I'm good with it. But when compared to the older gas Super Duty, Excursion, Diesel Suburban I owned, its fine. And plenty of power for me and what I use it for. It rides great, feels strong and is easy to use, especially with my trailer. From the rear cameras to the trailer light test while I'm standing behind the trailer. I am very pleased so far with my purchase and hopefully it remains that way. 

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5 hours ago, cfc said:

2020 HD LT Crew Cab, 4x4. 4k miles, 4 months old. 6.6 gas, 20" wheels. Very stable platform for me when pulling my 33' RV, 7k empty. Gas mileage 12-15 average, 7-9 when towing. Mostly country roads. I didn't purchase this 7k lbs truck for the mileage so I'm good with it. But when compared to the older gas Super Duty, Excursion, Diesel Suburban I owned, its fine. And plenty of power for me and what I use it for. It rides great, feels strong and is easy to use, especially with my trailer. From the rear cameras to the trailer light test while I'm standing behind the trailer. I am very pleased so far with my purchase and hopefully it remains that way. 

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I’m itching to hook my tt up and pulls some hills near me . It’s total length is 35.5 can’t remember box size . Dry is right at 7700 . Gvwr is 9500 but I’m sure we load it past that sometimes. Heaviest equipment load I’ve recently pulled was around 14,000 with my 07 . It did it great on interstate between 70-75 mph and got better mileage than my TT because of wind resistance. As soon as I get to I’m gonna load it up . I use to pull 18,000 regularly with a 1979 K10 with a 383 on back roads . That was always fun listening to that engine talk but I kept the speed below 55 because I overloaded a 92 k1500 once and the tail spun the dog around . No injuries but a wild ride

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How's the 6 speed transmission with the 6.6 v8? Any concerns? I have a 6 speed on my 2017 GMC 1500 and nothing but issues. I am sure it's a different 6 speed on the 2020 2500HD. 

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Your 1500 is different-you are right,  I hated my 2017 GMC 1500 6 speed transmission and only drove it 2100 miles in 2 1/2 years. They set that 1500 up for fuel economy and torque management and the only thing that would make it better is a programmer. With that said the new gas in the HD trucks with the 6 speed is a lot smoother. It could use a couple more gears. Ford has the 10 speed and Ram has the 8 speed. I drove the Ram and the trans was slick. Also with the new HD gas GM didn't install all that crappy fuel economy stuff like deactivation cylinders, torque management among others. I just love the small block 400 and V8 technology from 1955!!

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On 2/11/2020 at 3:26 PM, Morenar said:

How's the 6 speed transmission with the 6.6 v8? Any concerns? I have a 6 speed on my 2017 GMC 1500 and nothing but issues. I am sure it's a different 6 speed on the 2020 2500HD. 

It’s awesome . Stays in 5th towing my TT

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I raised the hitch 1" from 2016 2500 setting because bed clearance towards back of bed was too close for my taste. As a result it is slightly nose high but I am not observing any temp. differences in the trailer tires frony to rear. I have the curt 16 slider from my old truck. Truck gets better mileage on flat ground towing in 5th at 65 to 68 mph even when it will pull in 6th without downshifting. A result of rear diff gearing I assume.

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7 hours ago, ewbldavis said:

How is it off the line with the 3.73? Can't beat the 4.10 when pulling from a light - but drooling over the 2020's.

 

It will smoke the 6.0 with 4:10 probably at a little over half throttle . I’m not sure about when you up to speed. I drive a 2018 6.0 service body and my 2020 6.6 everyday. It may be just the way the truck feels but it has more power at lower rpms but at higher rpms it loses its punch some where the 6.0 gets in its main groove . My 08 6.0 feels like the race is on between 4000-5500 and really starts to talk . The 6.6 does it way before that. I love my 08 still haven’t decided if I’m gonna sell it or not but it feels like it barely moving down low in comparison then gets all nasty once it’s reved up. With that said 14,000 of equipment doesn’t feel anywhere near what the 08 could max tow in SC . My travel trailer with the wind resistance definitely strains it more . It’s a LB crew cab with a 6 inch lift and 35x12.5 mud tires 

Edited by Carolina
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GM really missed the mark on this application with the displacement and transmission when ford has the 7.3 and a 10 speed.  4.30 rear also available on the Ford. 

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