'22 3500HD Denali question

[laknox]

Since I haven't yet towed with the '22 3500 Denali, does the L5P have a "sweet spot" like the older Duramaxes do? My '02, when towing, seems to have a sweet spot right about 62 mph, max. I lose 1-1.5 mpg towing at 65. First tow will be in 2 weeks, so I'll see how it goes. I'll stick with 65 and see. Endurance tires are 81 mph rated, so no issues there.

Lyle

[Cummins12V98]

Put it in drive, hit cruise and enjoy the ride!!!

[4x4ord]

^^^ You’re in for a treat.

[laknox]

4x4ord wrote:


To loose about 1/2 mpg due to increasing your speed from 62 mph to 65 would be expected on account of the increased drag. Loosing more than that would be from the engine running at a less efficient rpm. But, increasing an engine's rpm by 5%, so say from 1500 rpm to 1575 rpm) you sure wouldn't expect to see its efficiency drop by 5 or 10%. Two basic rules that apply to fuel economy are:
1. a diesel engine is efficient at making power when loaded heavy .... higher rpm at a lighter load costs fuel.
2. turbo diesel engines tend to be most efficient at about 1700 rpm.
So although a heavily loaded engine might be most efficient at 1700 rpm a heavily loaded engine at 1300 rpm might be more efficient than a lightly loaded engine at 1700 rpm.

Towing my old '04 Komfort 26FSG (10' tall, 29'3" long, 1 14' slide, 11,360 GVW and just a square box) and my '17 KZ 277RLT (12'4" tall, 31'8" long, 3 slides, 10,500 GVW and a lot more "curvy") is an amazing difference. The height and length difference seem to actually help me. The KZ is, flatly, more aerodynamic. It's much easier to tow with my '02 than the Komfort was, for sure. Yeah, the KZ's lighter and we load light, but it tows so much better on the flat than the Komfort did. Same speed, same route, no wind, the KZ gives me better mileage. Can't wait to see what the '22 does!

Lyle

[4x4ord]

laknox wrote:
Since I haven't yet towed with the '22 3500 Denali, does the L5P have a "sweet spot" like the older Duramaxes do? My '02, when towing, seems to have a sweet spot right about 62 mph, max. I lose 1-1.5 mpg towing at 65. First tow will be in 2 weeks, so I'll see how it goes. I'll stick with 65 and see. Endurance tires are 81 mph rated, so no issues there.

Lyle

To loose about 1/2 mpg due to increasing your speed from 62 mph to 65 would be expected on account of the increased drag. Loosing more than that would be from the engine running at a less efficient rpm. But, increasing an engine's rpm by 5%, so say from 1500 rpm to 1575 rpm) you sure wouldn't expect to see its efficiency drop by 5 or 10%. Two basic rules that apply to fuel economy are:
1. a diesel engine is efficient at making power when loaded heavy .... higher rpm at a lighter load costs fuel.
2. turbo diesel engines tend to be most efficient at about 1700 rpm.
So although a heavily loaded engine might be most efficient at 1700 rpm a heavily loaded engine at 1300 rpm might be more efficient than a lightly loaded engine at 1700 rpm.

[Grit_dog]

You have 5 more gears, different final drive ratio and way more power in a largely different engine.
I wouldn’t expect it to be the same due to the truck but most fuel mileage drop is due to wind resistance and that’s not 1-1.5mpg @3 mph different.
Although 65 or below, if you can keep from losing your mind driving that slow is bout the best you’ll do.

[corvettekent]

It looks like we have very similar trucks. I tow at 65 MPH but I'm not sure that's the sweet spot, I get around 10 MPG while towing.