1500 miles towing | comparing to ecoDiesel and Cummins

[steiny93]

Did the first long distance tow with the wife's Denali dMax.
Pulled a Ranger 621 (just under 5000lbs) from Fargo ND to Lake of the Ozarks in MO, 750 miles each way.
Typically I'm using either a Ram ecoDiesel or a Ram 3/4 Cummins, using the Denali was a bit of a change up.

90% of the trip is on interstate, so cruise set 5mph over the speed limit (85 - 75mph). The Denali did a good job pulling the boat and the mileage was very good (15.2 mpg for the entire trip).
The dMax edged out the ecoDiesel (14mpg is typical) and the Cummins (13mpg is typical) in the mileage department. I'd give the dMax a slight edge over the ecoDiesel in the power department as well. From a ride perspective the Denali was head and shoulders above both (all good so far).

No oil usage; same level as when it left.

The DEF usage was crazy high (8.3 gallons of DEF to 1500 miles). Which in itself I can live with, using a lot of DEF, no biggie, just watch the gauge and you'll be fine.
ecoDiesel and Cummins would have used maybe 3 gallons each, leaving with a full tank would easily get you back.


But...
Here is where GMC messed up, and they messed up big time.
After say 600 miles of towing the truck had more then 1/2 tank of DEF and it went into limp mode because it didn't think it had enough DEF to continue. I was on the side of the interstate (in the rain) dumping in a 2.5 gallon jug (of which all 2.5 gallons didn't even fit as the tank wasn't even under 1/2 full).


So how did this happen, don't you get a warning message?
The dMax went from full DEF and full fuel to limp mode at 3/4 full of diesel at the next tank. The 'warning' was you have 299 miles DEF range remaining, then within 10 miles limit mode kicked in.

Called the dealer, yep, it's normal, they said to keep a jug in the back of the Denali.

 

[B-train]

Yay for emissions....

 

[B-train]

Good info nonetheless. Pretty good mpg given the load and speed

 

[steiny93]

Good info nonetheless. Pretty good mpg given the load and speed

Totally happy with the mileage, especially with the speed and the wind in play.

 

[dbphillips]

We got the messages on a trip with our travel trailer and kind of freaked out and were going to go into the dealer to see what was wrong, but it's just a bit of an overkill in the programming. As I recall, you can actually go 500 miles past when the computer thinks you are out of DEF before it reduces speed limit to 65, then another 250 or 500 before true limp mode. Now I just ignore it. But I do keep a jug in the back anyhow.

 

[steiny93]

We got the messages on a trip with our travel trailer and kind of freaked out and were going to go into the dealer to see what was wrong, but it's just a bit of an overkill in the programming. As I recall, you can actually go 500 miles past when the computer thinks you are out of DEF before it reduces speed limit to 65, then another 250 or 500 before true limp mode. Now I just ignore it. But I do keep a jug in the back anyhow.

interesting
This one did "you have 299 miles" warning to idling on the interstate within 10 miles of the 299 warning (with the DEF tank being over 1/2 full).

 

[dbphillips]

interesting
This one did "you have 299 miles" warning to idling on the interstate within 10 miles of the 299 warning (with the DEF tank being over 1/2 full).

Yeah, I got down to basically no DEF last week on our long term trailer trip and our LM2 said 500 miles to 65 MPH limit, so confirming. I guess you must have LZ0? Hope they don't change our software. I'd be forced to take more drastic action.

 

[Stbentoak]

Just did 400 miles yesterday... avg 28.5 MPG at 80 MPH. Diesel still .30 Cheaper than premium and 50% better mileage. Better than a Camry. Happy.

 

[steiny93]

Over the weekend we did a 1000 mile towing trip with the EcoDiesel instead of the Dmax pulling the same boat as in the original post above.

EcoDiesel did 14mpg and the def gauge didn't move over 1000 miles. Crazy how the def consumption is so different.

 

[8mmag]

No towing for me...yet.
Just before my 36K warranty expired I had mine in for 3 issues, DEF indicator issues being one of them.

On mine, I had a situation where 1) the DEF gauge read Full, 2) the 1000 miles to reduced speed came on on the dash, and 3) I stopped to add DEF and could only add about 2 gallons before it overfilled out the vehicle, so the tank was over 1/2 full.

So the gauge was reading high and the DEF warning said I was low. The dealer said they 'reprogrammed/recalibrated' the system.

2000 miles later (not enough to know if that resolved the issue), I have not had the problem re-occur.