Towing fuel Economy

[AH64ID]

The instantaneous mpg will probably be better than egt for economy. That being said I do like having the CTS2.

 

[John Jensen]

My first towing with my 2020 3500 HO Aisin pulling my 9000+ lbs trailer was 9.56 mpg hand calculated. With only 3000 miles on the truck and running 65 mph through the mountains and 70 mph on the desert, I'm pleased. As this truck breaks in it can only get better

 

[AH64ID]

With all this talk of towing on new trucks I thought I’d mention the recommended break-in for the truck, which mostly applies to the gears.

No towing during the first 500 miles, and 50mph max during the first 500 miles of towing.

Take that for what you will. My truck has about 4200 on it for my first tow and it took until 5700 miles to accumulate 500 miles of towing. I wasn’t as dedicated to the speed restriction due to the truck having some miles on it already, but due to the nature of where we camp many of those miles were under 50 mph. The last 100 or so of the 500 mile break-in were not as we were cruising on the interstate.

With that in mind I highly recommend an early change of the rear diff lube. I’ve heard it’s better on the 19+ trucks, but the OEM stuff still has a lousy reputation. I changed mine at 15K miles and I’ve never seen such nasty gear lube with so few miles. It was far worse than the gear lube I just changed on my wifes 4Runner that had 100K miles on it.

 

[Killer223]

Interesting results and read.
I'll add mine.
My early 04 would regularly get 16-19 empty and 12-14 towing a flatbed with SXS on it and 7-10 towing a 34' 5th wheel at 13K.
my deleted 08 was hands down better MPG wise then my 04 ever dreamed of getting. same loads and it was easy 2-3 mpg better.
Same basic truck. 04 is qqLB built 48re, 08 was mega G56. same wheelbase, same tires, same gear ratios,
The power of the 08 is what made it tow so effortless. the engine wasn't' working towing a load. where the 5.9 is working hard to tow same loads.
all loads are at 70 mph.
Same oil in both trucks, same rear dif oil, although the 08 had a antispin and the 04 was open, I believe this is why the 08 went through tires faster.
Both trucks had over 200K, with the 04 over 300K now and i sold the 08.

 

[Dick Langendorff]

Yes. In the Hemi I usually ran 62 in CA as the fuel economy really dropped off at 65+. With the diesel it still drops off at higher speed, just not as bad as the Hemi.
We towed four quads to Colorado with a car trailer this October and got 12.47 calculated but we ran 80mph in most of Nevada and Utah across the salt flats. Lots of idling in the cold in Colorado.

Under those conditions, you’re doing well. I usually cruise CA at 60/62. Nv, Ut, Wy, closer to 67/68. On a 5000 mile trip I’m 13+. Leave with a full tank, go to the same station when I get home and fill up. Then use the calculator.

 

[Cummins12V98]

Speed kills!

I can be double towing my 35k combined at 60 and easily get 9.5 mpg on flat roads with no wind. Bump that to 70 and it's around 8.

 

[Ozymandias]

The 2020 will weigh more but not by too much. Hp isn’t much different either.

I can’t monitor EGT with the dash. That was handy when trying to get best fuel economy. Getting a baseline for the IMAP sensor is a good idea too as it will get bunged up with soot sooner or later. Exhaust back pressure sensor is another one critical to efficiency and hp. Not worried about “derates” its not like I’ve got a backwoods truck hacker tuning it...

EGT says absolutely nothing on a 18+ Truck as the EGT is set by the ECM to keep the DPF and SCR system happy.
You can't even idle it down as the temps stay way up even idling.

 

[slowmover]

Took my truck on its first trip towing. 25L/100km or 9.4 USmpg. My 03 6spd would do 15 USmpg easily. Not a heavy load nor not aerodynamic. I knew an automatic, emissions and heavier truck would hurt mpg but this was a bit disappointing. I was a bit disappointed in when you hit resume for the cruise it hunts several gears instead of just accelerating properly. My 1500 with 8spd doesn’t do that. It’s too bad that there is no aftermarket tuning for the AISIN.

What is rpm sweet spot for fuel efficiency?

You’ve seen me write it before, so here’s another go at it

No one tests for baseline which is to remove both driver & aero penalties. What’s the towing mileage is a percentage penalty.

1). Cold air pressure tire reading after sitting overnight.

2). Preferably 45-50 miles to a segmented truck scale (CAT Scale). Get phone app.

3). Top off fuel to first auto-shutoff. Farthest fuel pump best.

4). Truck solo but with only permanent gear aboard get the scale reading.

5). Correct tires to actual load values against Load & Pressure Table (and inside Dodge range).

6). Hit Interstate cruise control ON immediately set on 58/9-mph maximum to avoid aero penalty AND take driver out of equation.

7). Use an isolated (deserted) turnaround about 100-miles out. Return to same fuel pump and refill to first auto-shutoff.

At 200-miles at 16-MPG it’s only about twelve (12) gallons. Not a substantial enough test, but it’ll suffice for the unskilled who panic at running slow (yet still legal). Farther is FAR better.

A). Now have an accurate TARE weight. Truck will never be lighter.

B). Now have an accurate tire pressurization (check at trip end. 7% pressure rise about right. 10% needs just a few more puounds). Braking & Handling are optimized. As is tire life.

This is the ONLY accurate baseline. Your disinterested daughter could be the driver. No lane changes, no braking EXCEPT at turnaround.

What the truck is capable of in highway steady-state is HOW to diagnose ALL OTHER changes. Trailer weight doesn’t mean much, but aero sure does.

Handling, Steering, Hitch Problems, Brake Problems are all diagnosed from an established baseline. Which next to none of you has bothered with.

Really way out at sea by the time one is talking about towing fuel economy.

Have to start fresh and work forward.

Truck
1). Alignment
2). Brake Drag
3). Tire Pressure
4). CAC system
5). Steering Gear

Trailer
1). Alignment
2). Brake Drag
3). Wheel Bearings
4). Hitch concerns (rotation on axis)

All maintenance (both vehicles) to book standard TIME not just miles.

Scaled results: NO trailer should lighten the steer axle

Kenworth & Cummins BOTH regard Steering Wherl Corrections per 100-miles a significant parameter.

4WD has terrible steering. And shocks never last much more than 40-60K miles (gas charge leaked out), so that combo along with improperly-chosen highway tires accounts for the majority of why truck spec matters greatly in MPG analysis.

If one is serious, MPG is chasing tenths. After verifying mechanical condition and installing proper tires

If I can fill my tank and run an average distance at 80% tank capacity of 430-miles with my 35’ travel trailer it’s more than just truck spec.

KW & Cummins also cite these factors (in order of importance):

A). Truck Spec
B). Climate
C). Terrain
D). Operator Skill

If I can get in your rig and get better MPG than you ever have (pretty close to a sure bet; same conditions applying), it’s because it’s worthy of your time and miles to experiment. Your studied effort.


Clue #1

Travel Speed. Nothing above 65-mph is ever economical. “Saving time” is an irresponsible child’s answer. The combined rig won’t have functioning trailer brakes before completing an emergency stop.

There’s NO significant time savings on a sub-300 mile trip makes above 64-mph beneficial. Shortens engine life. Tire life. Can’t stop. Can’t maneuver.

That realization cuts off the idea that it’s up to the driver. Ha! Machines and road designs have limits.

Are you ever less than 100-yards from the vehicle ahead? Because you sure as hell won’t make a full emergency stop in that distance.


Clue #2

What’s your average full-on emergency stopping distance when hitched to THAT trailer?

Start asking responsible questions and FIND responsible answers. Test. Verify. Modify.

FUEL ECONOMY will (literally) fall into a range where it doesn’t change much.

The working range for a pickup is from 55-65/mph.

The best engine rpm for FE will be somewhere near peak TQ below 60-mph The gear split to get above that is second-best.

Computer-control of variable-vane turbochargers and multi-speed automatics changes this but little.

Detroit has been screwing you pickup owners for almost twenty years now. The trucks are no more powerful, and get no better fuel economy than the first CR model.

In contrast, this Peterbilt I’m sitting in is far better in FE than it’s early CR counterpart.

When I’m empty I rarely fall into single-digit FE. That’s 35,000-lbs of truck & trailer.

Bobtail, this 19,000-lb tractor cruises at 14-MPG.

YOU CANNOT FIGHT CITY HALL (computer control). So focus on proper tire spec, driver skill, and safe operating limits.

Virtually no one drives with safety in mind any more (don’t include yourself, it’s the rarest bird to be seen any more; I’ve been crossing America by vehicle since the JFK years), but if you do you’ll see MPG come way up.

MPG (and tire life) are just indicators of operator skill. Tires should last 100k and brakes even longer. Average MPH should be in the low 30s at a minimum.

A Cummins is pretty much a 10,000-gallon engine. That’s the marker. Burn it up too soon and lose the best thing it had to offer. (350k life average).

ECONOMY is a mindset.

Get the baseline numbers.

.

 

[Bug Out]

With all this talk of towing on new trucks I thought I’d mention the recommended break-in for the truck, which mostly applies to the gears.

No towing during the first 500 miles, and 50mph max during the first 500 miles of towing.

Take that for what you will. My truck has about 4200 on it for my first tow and it took until 5700 miles to accumulate 500 miles of towing. I wasn’t as dedicated to the speed restriction due to the truck having some miles on it already, but due to the nature of where we camp many of those miles were under 50 mph. The last 100 or so of the 500 mile break-in were not as we were cruising on the interstate.

With that in mind I highly recommend an early change of the rear diff lube. I’ve heard it’s better on the 19+ trucks, but the OEM stuff still has a lousy reputation. I changed mine at 15K miles and I’ve never seen such nasty gear lube with so few miles. It was far worse than the gear lube I just changed on my wifes 4Runner that had 100K miles on it.

I know the Manufacturer has said "good to tow" right off the floor. I have never done that, and always gone the traditional 1000 miles empty before towing. Varying RPM's along the way. Thus far, I have not had any issues as I have read about here with AAM's noise etc. Hoping the same for the new truck. Going to change out gear lube at 10K go to Amsoil as all the other trucks have had with zero issues.

 

[CToney]

Points noted. I’ll change rear diff oil after break in. I bought the truck to tow. I have owned the truck for 2 months and towing was my first drive with it. Can’t turn back time so I won’t lose sleep over it. I have a Ecodiesel for a car truck, thank goodness.

I’m guessing running in 5th gear at 60-65 mph might yield the best mpg. I’ll do some testing. Probably should have ordered truck with 4.10 gears...

Optimized ECM programming would no doubt improve fuel efficiency. I guess I need to learn how to use Calterm...

 

[AH64ID]

Can’t get 4.10’s on a SRW so no issue there.

Give it a little time and it will likely improve a little.

Maybe a brake is dragging on the trailer, so the truck had to work harder than with your 3rd gen.

There is probably a little efficiency left on the table from tuning, but not much and at the cost of your warranty. Does caltrrm let you modify tables, or just use already published tunes?

 

[Ozymandias]

You really consider tampering a new Truck under warranty?
You know they will get you, there is no such thing as "leaves no trace" on these vehicles.

 

[Cummins12V98]

OZY is correct, per MayMadnessStan Gozzi they said they may not know what you had but they know you DID have something and poof goes your warranty.

IMHO get the junk diff fluid out of there before 5k and replace with the appropriate AMZ/OIL SevereGear.

 

[Wiredawg]

My towing mileage GCW varies between 7.5 and 9.6 MPG almost 34K Lbs and I'm happy with it... best solo 11.6MPG.... typical solo mileage 10.2.

EDIT: I tow 65 MPH and solo drive 72 MPH...

Christmas Cheers, Ron

 

[Jebruns]

My trailer is not that heavy at 7-8k, but I live in the Ozarks Mts. So not huge pulls, but lots of up and down. I'll paste in a 40 mile stretch of GPS altitude changes below. Anyway, I haul at 77-80mph and get 9.5-10mpg. Which I'm fine with. Much better than the gas 3/4ton I had before my Ram/Cummins, and I could not drive at the same speeds either.

 

[Bug Out]

Points noted. I’ll change rear diff oil after break in. I bought the truck to tow. I have owned the truck for 2 months and towing was my first drive with it. Can’t turn back time so I won’t lose sleep over it. I have a Ecodiesel for a car truck, thank goodness.

I’m guessing running in 5th gear at 60-65 mph might yield the best mpg. I’ll do some testing. Probably should have ordered truck with 4.10 gears...

Optimized ECM programming would no doubt improve fuel efficiency. I guess I need to learn how to use Calterm...

I'm sure it will be fine. I just am quirky about break ins. I know the big 3 have been trying for years to convince the public they make the best etc, no break ins ...4:10's are ok, but to be quite honest, if I had the ability to choose when i bought, I would have went 3:73. My 4:10's in this truck do give me 33400 towing capacity and 43000 GCVW from the factory, but I'd prefer less RPM's then 2K at 72mph. I tow max at this point 17K. My 16 3500 SRW with 3:42's did fine, but the new 5th put the SRW over the max edge.Had to go dually again. This truck was staring me in the face begging to go home with me.....

 

[Wygate]

I notice everytime I plug my trailer cord in my mileage is cut in half..think I'll hook up to trailer and not plug cord in next time...

I was thinking it was just me!

 

[CToney]

I had a loaner from the dealership while my LED headlights get installed. 2016 Ram 1500 hemi. 4x4 5’7” box with bed cover. Fuel economy not much better than my 3500. I guess I shouldn’t complain. Ram better pull their socks up on gas 1500s though. Mileage on other pickups rivals my Ecodiesel.

FYI truck had air suspension which threw error codes on my way home. It didn’t ride much better than the coils in my ED.

 

[GBergen]

I know the Manufacturer has said "good to tow" right off the floor. I have never done that, and always gone the traditional 1000 miles empty before towing. Varying RPM's along the way. Thus far, I have not had any issues as I have read about here with AAM's noise etc. Hoping the same for the new truck. Going to change out gear lube at 10K go to Amsoil as all the other trucks have had with zero issues.

While I agree with your strategy for Break-in, this is in the 2021 owners manual: I couldn't find this information in TDR using Breakin, Break-in or Break in search criteria. Maybe it's just me... That said, I plan on doing some thing that's somewhere in-between the information in the post above and the mfg recommendation. Maybe I'll take the utility trailer with the UTV on it for a trip around the hills in southern Idaho.. Then a little later, hook up the empty TTL for a similar trip.

ENGINE BREAK-IN RECOMMENDATIONS —
DIESEL ENGINE
The Cummins® Turbo Diesel engine does not
require a break-in period due to its construction.
Normal operation is allowed, providing the
following recommendations are followed:
 Warm up the engine before placing it under
load.
 Do not operate the engine at idle for
prolonged periods.
 Use the appropriate transmission gear to
prevent engine lugging.
 Observe vehicle oil pressure and temperature
indicators.
 Check the coolant and oil levels frequently.
 Vary throttle position at highway speeds
when carrying or towing significant weight.
NOTE:
Light duty operation such as light trailer towing
or no load operation will extend the time before
the engine is at full efficiency. Reduced fuel
economy and power may be seen at this time.
For additional vehicle break-in requirements
see page 241.
Because of the construction of the Cummins®
Turbo Diesel engine, engine run-in is enhanced
by loaded operating conditions which allow the
engine parts to achieve final finish and fit during
the first 6,000 miles (10,000 km).

from page 241:
 Do not tow a trailer at all during the first
500 miles (805 km) the new vehicle is
driven. The engine, axle or other parts could
be damaged.
Then, during the first 500 miles (805 km)
that a trailer is towed, do not drive over
50 mph (80 km/h) and do not make starts
at full throttle. This helps the engine and
other parts of the vehicle wear in at the
heavier loads.