New 2016 Denali 3500 Diesel / MPG

[ted 95]

Hi All
Well one thing at a time. Got home this week to the land of the frozen tundra. Montreal. Well we wrote the check and picked up our new truck. It has been sitting at the dealer since January. Can I get some opinions as to how long it takes for the LML engine to break-in so the MPG gets to within reason. By the way this monster is sweet. My reading material has been the 300 page plus manual for the last 5 days.
Now we have to finalize the sale of the Florida house and get the RW ordered. Hope this happens fast as we want to go to the Rally in August.

[Char & Steve]

Don't have a lot of input yet except it tows great!
We have about 6500 miles on it and when I hauled the RW back from the factory with only 1500 miles it was averaging 11-12. Around town here we get about 16.

Steve

[rlmankin]

I have about 47k miles on my 2013 Denali, so it is not quite broken in, but close. To date, mpg numbers under various loads and driving conditions are below:
unloaded, long distance freeway driving (75-80 mph) - 19 to 20
unloaded local driving - 15 - 16
towing boat (~ 3500 lbs), mountain driving - 11.5 - 12.5
towing the RW31sl, light headwinds - 10.5 - 11.5
towing the RW31sl, heavy headwinds or mountains - 8-5 - 10.5

Mountains are no problem with tow/haul and exhaust brake on. Those are the main reasons I purchase the GMC. Hope that helps

[spindrift]

Originally Posted by rlmankin

I have about 47k miles on my 2013 Denali, so it is not quite broken in, but close. To date, mpg numbers under various loads and driving conditions are below:
unloaded, long distance freeway driving (75-80 mph) - 19 to 20
unloaded local driving - 15 - 16
towing boat (~ 3500 lbs), mountain driving - 11.5 - 12.5
towing the RW31sl, light headwinds - 10.5 - 11.5
towing the RW31sl, heavy headwinds or mountains - 8-5 - 10.5

Mountains are no problem with tow/haul and exhaust brake on. Those are the main reasons I purchase the GMC. Hope that helps

Is this a SRW or DRW set-up?

[Tomkidder]

It took my Cummins about 40-50 thousand miles to break-in. Keep Dino oil in it for the first 50,000. Then make the switch to full synthetic. If you have the money first thing to put into the unit is a set of gauges to watch EGT's. Chronic Hight EGT's during the first 50,000 is a killer.

[5th_Time]

Towing 36RL mostly highway 10.5 to 11.5mpg.

[Shane Wood]

I have 8600 miles on mine and running 75-80 highway, empty 16 mpg. when new on 5000 mile trip pulling I averaged 10 1/2 mpg

[rob_fla]

Originally Posted by 5th_Time

Towing 36RL mostly highway 10.5 to 11.5mpg.

That is about the same fuel mileage I get with my 2012 GMC 3500HD DRW pulling my 38FL (currently have approx. 60,000 miles on my GMC)

[travelin' texans]

That's about the same as my '13 with 71k towing at about 68mph/1700rpm which is the sweet spot on mine. I've heard others that get 14-16+ towing, not doubting their word, but they are also towing 55-60 mph, I try to stay near the speed limit. IMO if you can get 11-12mpg with any of the brands that's not too bad.

[RWJSIM2003]

On our 2008 F450 I am getting 14-16 when not towing and 12-11 towing 65-70mph. that is with the tuner set on Medium.

[rlmankin]

I'm sorry I thought I had posted a response. This is a SRW.

[RCAircraft]

Originally Posted by ted 95

Hi All
Well one thing at a time. Got home this week to the land of the frozen tundra. Montreal. Well we wrote the check and picked up our new truck. It has been sitting at the dealer since January. Can I get some opinions as to how long it takes for the LML engine to break-in so the MPG gets to within reason. By the way this monster is sweet. My reading material has been the 300 page plus manual for the last 5 days.
Now we have to finalize the sale of the Florida house and get the RW ordered. Hope this happens fast as we want to go to the Rally in August.

Our 2016 Silverado High Country 6.6 diesel crew cab, 3.73 gearbox with a long bed had a stated 500 miles at or below 55 MPH and no towing in the owner's manual. That goes by fast unless one is inching to hit the road!

[travelin' texans]

Originally Posted by RCAircraft

Our 2016 Silverado High Country 6.6 diesel crew cab, 3.73 gearbox with a long bed had a stated 500 miles at or below 55 MPH and no towing in the owner's manual. That goes by fast unless one is inching to hit the road!

Mine had about 50 miles on it before it got hooked up to the RW & towed 300 miles at 68-70 mph, 72k later I guess it didn't hurt it. I was always told to break it in like you intend to use it.

[xtasee]

Originally Posted by travelin' texans

I was always told to break it in like you intend to use it.

I believe that that statement is for the engine. The gears are the issue for the conservative break-in procedure.

[spindrift]

Originally Posted by travelin' texans

I was always told to break it in like you intend to use it.

And you were told correctly. One of the biggest fallacies going, at least with a diesel, is the "tread lightly" school of thought; baby the thing for "X" number of miles and then you're good to go. Back in the day, when I was rebuilding Cummins engines, those trucks were immediately taken to the dyno after a rebuild and those engines were brought to their knees. I don't ever remember being told to baby the thing.

[Shane Wood]

My manual said no towing first 500 miles. At 620 hooked up and pulled for 5600 miles between 62 and 70mph

[xtasee]

Originally Posted by Shane Wood

My manual said no towing first 500 miles.

Rear axle protection only. The ring an pinion gears need to have a proper wear pattern before adding additional stress. JMHO.

Larry

[Shane Wood]

In all my years of towing from utility trailers to 80000 lbs I have not heard of this about a differential. The only time I have ever had differential problems was 4 wheeling in the mountains and abusing the living sh!! Out of them. I did this for years. Can you explain more about this
Thanks

[piper guy]

I agree with Spindrift on running a diesel. I run a lot of boats in the 50-70' range with big Cummins or Volvo diesels. Right from the start they are turned up to 90% and sometimes we run all day at that setting for 8-10 hours. Never had any problems and the Cummins reps I have talked to said "run it like you're mad at it"

[Ford truck guy]

I drive it, like I stole it after a couple hundred miles I am good to go... I was always taught to break them in the way they will be driven...