i took a 200 mile trip towing a 25 foot v nose trailer that was 5000# loaded, tow haul mode on cruise set at 65 mph, rpm about 1900,the truck got 9.6 mpg hand caclculated. on the way home had the same load 200 miles tow haul mode off cruise set at 75mph,rpm around 1750,the truck got 9.2 mpg hand calculated. does the tow haul mode keep the truck in a lower gear? i found it odd to run a lower rpm while going faster mph. either way i am not happy with the results. i assumed if i kept it at 65 mph or below i would have seen better(at least 10 or 11mpg).oh well it is what it is lol

What was the wind doing on each leg of your trip?

Those numbers seem awfully low either way.

1750 @ 75MPH ? I can't do that empty on a calm day. Completely stock I see 1800 @ 68 - 70mph. What tire size do you have?

there was 15mph crosswind both ways, i am running 285 bfg a/t ,completely stock,new fuel filter,stanadyne every tank,miles were calculated to compensate for the 285s

Where do you live? Winter blended fuel and cold temps can drop mileage. I drop from 1 to 2mpg in the winter (empty truck).

Jay

wow those numbers seem low...any programmer?

wow those numbers seem low...any programmer?
no programmer yet,i live in oklahoma and it was a 45 degree day

Does tow haul even work in 6 th gear at 75 mph, cant recall anyone ?

Seems low for what you were pulling. I got about 12.7 MPG pulling a small camper at average speeds around 70 MPH in hilly terrain. I did some quick take offs a few times merging onto the interstate, so that hurt the mileage too. It was not the weight that zapped my mileage, but the wind resistance, due to the height of the camper. Its an older camper and its about as aero as a brick.

Ive gotten as good as 14mpg pulling my 25ft trailer at 65mph WITHOUT a headwind or hills. However as soon as I push 70mph the mileage drops to 12 or 12.5. While driving at a desired constant speed in cruise with towhaul I cancel my DIC/mpg and let it boot-up for an instant rate. I'm often surprised at how a headwind or a couple mph effect mileage so I adjust accordingly. In the mountains I just drive and take mpg as it comes watching temps and the road. This DMax still beats up on any gasser in mileage that I've ever had - AND IT"S FUN !

it will go into 6th, but i think its around 65 to 70 mph

no programmer yet,i live in oklahoma and it was a 45 degree day


nice to meet a fellow okie!

your not going to get great mileage towing especially with oversize tires and winter fuel. just think if you had a gas engine of similar size say a 454 you would get about 4-5 mpg in your situation.:p:

A 25 foot 5,000 lbs trailer at 65 MPG getting 9.6 mpg and then on the way home you drove 75 MPG and got 9.2 MPG. Thats about 12,500 lbs rolling down the highway at a pretty high speed.

What kind of mileage do you think you should get?

I get 14.5 mpg with Lance 11.6 camper on 06 LBZ 3500.

FYI my old 454 gmc (Built to work 400 hp) used to get 10mpg with camper and dirt bike trailer.It seems that efficient gassers can haul well as long as they have the torque.But nothing out torques a duramax.

Speed and headwinds have a big effect on mpg.
Dually club 481:rant:

That does seem a little low. When I pull my high profile Fifth Wheel ( 37' long and average weight of 12,500 lbs) I get right at 10 mpg driving 60 to 65mph. When I tow my utility trailer with tractor and 4 wheeler on it for a total weight of approximately 5,000 lbs, I get just a bit over 15 mpg. That is all hand calculated and I always use tow mode when towing. Personally, I think the height of trailer and/or wind resistance hurts mpg more than weight.

agreed with all above. seems V Low. How old is the truck, milaeage, mods etc...(oh yea, that is usually what one would see in a sig..??).

Anyway, mild sarcasm aside..I pull every summer, a 5000lb trailer - no V nose for sure and typically get 12.6 pulling in the Rockies. I don't use tow haul except for some very slow torturous turns in the Golden BC area. I have always thought that tow haul is one gear down from D. Avg speed 60-65 and up to 75 on freeway for about 100 miles of said trips.

Seems low for what you were pulling. I got about 12.7 MPG pulling a small camper at average speeds around 70 MPH in hilly terrain. I did some quick take offs a few times merging onto the interstate, so that hurt the mileage too. It was not the weight that zapped my mileage, but the wind resistance, due to the height of the camper. Its an older camper and its about as aero as a brick.

Btw I am all over BIGR's post above. X2 for sure.!

cheers,

stk

I always use tow haul but you have to be at about 60 to 65mph on a flat for it to kick into 6th. I take it out of tow/haul to get it to go into 6th then re-engage it. As I put more miles on the truck it drops into tow/haul quicker. That mileage is still pretty low although you might be using winter fuel. I would expect you to get around 13 MPG towing that rig at 65mph. At 75 though it is all out the window. BTW your tires on your trailer are only rated at 65MPH and if you get it flat it will cost you so you probably should stay at 65. The flat will rip the crap out of the trailer for sure.

What kind of mileage do you get when you're empty?

there was 15mph crosswind both ways, i am running 285 bfg a/t ,completely stock,new fuel filter,stanadyne every tank,miles were calculated to compensate for the 285s

is your speedo corrected? if not (and assuming you were going by the speedo read-ot) you were going faster than 65 and 75. more like 70 and 80.

I usually get 12-14 mpg pulling either my 4 horse stock (with or without 4 horses) or my 24' stock (with or without 10 horses.) I'm never seen single digit mileage, I think I would cry before screaming.

But then, Commifornia only allows trailers to go 55, so cruise is usually stuck at 60.

i took a 200 mile trip towing a 25 foot v nose trailer that was 5000# loaded, tow haul mode on cruise set at 65 mph, rpm about 1900,the truck got 9.6 mpg hand caclculated. on the way home had the same load 200 miles tow haul mode off cruise set at 75mph,rpm around 1750,the truck got 9.2 mpg hand calculated. does the tow haul mode keep the truck in a lower gear? i found it odd to run a lower rpm while going faster mph. either way i am not happy with the results. i assumed if i kept it at 65 mph or below i would have seen better(at least 10 or 11mpg).oh well it is what it is lol

My diesel mechanoc told me to NEVER tow ANYTHING below 2000 RPM
after chating with him for a while, I learned that My 06 duramax consumes more fuel when im under 2K RPM's ( loaded ) I was getting 9 to 10 mpg with a 35' toy hauler.

Now I get 14 to 15 with the same trailer, but now I run in 4th gear ( instead or 6th @ 1800) at 2900 RPM and arround 60 to 65 MPH.

he also stated that my motor is mutch happer at thoes rpms, and my EGT's went from 13's down to 10's

A 25 foot 5,000 lbs trailer at 65 MPG getting 9.6 mpg and then on the way home you drove 75 MPG and got 9.2 MPG. Thats about 12,500 lbs rolling down the highway at a pretty high speed.

What kind of mileage do you think you should get?
i would be happy with 11 or 12

What kind of mileage do you get when you're empty?
15 around town 17 to 18 on the hwy

is your speedo corrected? if not (and assuming you were going by the speedo read-ot) you were going faster than 65 and 75. more like 70 and 80.
speedo is not correct,mph were by gps

I got numbers close to that (OP's) pulling my 28ft race trailer running 75-80.
I think the 6 speed throws a wrench in the mix, the motor likes more rpms but to get it you're pushing more wind at higher speeds. Also I got the same mpg when the trailer was loaded or empty, a 3700 lb difference.

One thing I found was if I drafted an 18 wheeler I would pick up 2-3 mpg.

BTW, I'd get 18 to 20 on the hwy without the trailer.

9 mpg does seem pretty low, even with that size trailer. I was getting with my '05 LLY stock 13-14 mpg pulling a 24' hardside camper (~5000lbs) and with the Bully Dog Intake and DiabloSport tuner on Tow Mode was up to 16.5mpg and once 17.4mpg with a tail wind all the way home. When I'm towing I rarely look at the speedometer and just look at the tach. I try to keep it between 1800-2150rpms (up to 68 or 69mph) and that always seemed to be my peak performace zone.

Pulling 10600 at 70 MPH for 350 miles was good for 9.4 and the RPMS was around 21 to 2200

My diesel mechanoc told me to NEVER tow ANYTHING below 2000 RPM
after chating with him for a while, I learned that My 06 duramax consumes more fuel when im under 2K RPM's ( loaded ) I was getting 9 to 10 mpg with a 35' toy hauler.

Now I get 14 to 15 with the same trailer, but now I run in 4th gear ( instead or 6th @ 1800) at 2900 RPM and arround 60 to 65 MPH.


Very interesting! I'm doing 12-14 with a fifth wheel towing in 6th (60-65), but I find it very suprising that a diesel likes a higher RPM, especially since I think that is well above max torque (if I remember correctly).

thats kinda what i was thinking...running it above 2000 rpm's you would think thats way too high to run all the time...any experts have an opinion on running the d-max that high for that long

God!!!
I get that (10 mpg) with my gaser. Towing a 24 ft v nose @ 0ver 7000 lbs. I what to buy a diesel but was hopeing to get around 14-15 other wise it doesn't justify the cost differances.

Very interesting! I'm doing 12-14 with a fifth wheel towing in 6th (60-65), but I find it very suprising that a diesel likes a higher RPM, especially since I think that is well above max torque (if I remember correctly).
keep in mind that 1600rpm peak torque figure is at the engine. When you see most dyno runs, rear wheel torque peak usually tends to be in the low to almost mid 2000 rpms.

God!!!
I get that (10 mpg) with my gaser. Towing a 24 ft v nose @ 0ver 7000 lbs. I what to buy a diesel but was hopeing to get around 14-15 other wise it doesn't justify the cost differances.

I've never gotten near 10 mpg with my 97 3/4 ton 4x4 with 350 engine and 6-speed manual transmission carrying approx 7000 pounds. 7 was about the norm for that rig. Now I can pull the same load at about 14-15mpg with my 06LBZ. Empty, I could only get about 14 highway, and now I get 20-22 in summer with my LBZ.

keep in mind that 1600rpm peak torque figure is at the engine. When you see most dyno runs, rear wheel torque peak usually tends to be in the low to almost mid 2000 rpms.

I don't quite follow this. On a diesel engine, isn't max fuel economy and the *engine* max torque very closely correlated?

I'm not sure why maximal torque at the drive wheel would factor into fuel economy. For traction and breaking loose, it makes sense, but not for fuel economy in my mind. I mean, if you wanted max pulling power, you would want to pick the engine speed and gear that multiplies out to the most torque hitting the ground. Using your example above, I would assume that means 1600 rpm in the lowest gear possible.

Conversely, if you wanted the best fuel economy, in general, it means that you want the engine to be putting out the most torque, but at the lowest engine speed possible at that torque max, coupled with the fastest/highest gear ratio, matched up with a corresponding speed that (Aerodynamic) drag is not a overriding factor. On a gas engine, it (usually) means max vacuum, highest gear, lowest ground speed, and lowest engine speed. But gas engines usually build max torque high in the RPM range. On an unthrottled diesel, it would usually mean lowest speed at highest torque, which generally is relatively low RPM and a higher gear to take advantage of the higher torque.

But I'm just throwing out what I think factors into fuel economy.

I'm a little confused also. It seems to me the lower RPM's while towing would give better mileage. I think when I'm around 60 -62 mph my RPM's are around 1700. If I am understanding this right, when I'm towing, I would get better mileage by putting the trans in manual and downshifting to a lower gear to get the RPM's up around 2000 and still driving 60 - 62 mph. This is towing down the interstate without a lot of hills. Am I understanding this correctly?

With two quads standing up in the back of my truck, and towing a 25' travel trailer fully loaded with water, supplies, gasoline,etc., doing 75-80mph, I am getting about 9.5-9.8 mpg. I just set the cruise and enjoy the ride. However, empty I can easily get 19.5-19.8 doing the same speed. Not extremely happy with the mileage, but what can I expect when i'm towing a rolling windblock. Truck runs really strong with power to pass just about anyone, loaded...

I was always told that the shift points were different in the tow/haul mode, but the final drive was the same.

I tow a 10k 34' vnose at 75-80 and get 8-11 depending on the wind. Towed the same with my 02 and got 1-2 mpg better....go figure. Maybe will have to try the manual mode and higher rpms

I Avg about 9 towing a 26ft toy hauler over a 4100 ft pass at 70 mph 3200 rpm. The trailer weighed about 10,000 partcially loaded. I was beating on it pretty good though cause I got cut off by an Exploder and was showing him that I wasn't slowing the traffic down. I wonder why he couldn't pull away?:rolleyes: I Avg 11 going to Sand Lake, Oregon weighing 20,000 overall doing 65 mph most of the way.

I was always told that the shift points were different in the tow/haul mode, but the final drive was the same.

I tow a 10k 34' vnose at 75-80 and get 8-11 depending on the wind. Towed the same with my 02 and got 1-2 mpg better....go figure. Maybe will have to try the manual mode and higher rpms

Tow/haul mode locks the torque converter after 2nd gear, changes the shift points, enables cruise grade braking, and transmission assist braking (w/ TC locked). In tow/haul I find it patient to go into 6th, usually 62 to 65mph. Sometimes I will take it out of tow/haul to allow it to shift into 6th if I am running 62 - 65mph consistently.

I think that the crosswind had more to do with your fuel economy than anything else. The speed you were running should yield a higher MPG, most would agree all things remaining constant, but you did mention that you had a crosswind of 15mph, maybe more? That alone will suck down 1-2 mpg when you dont have a load at the same speed. These trucks arent exactly aerodynamic, more like a brick going down the road. Try dropping back to 65mph next time and I bet you will see 12-14's

My diesel mechanoc told me to NEVER tow ANYTHING below 2000 RPM
after chating with him for a while, I learned that My 06 duramax consumes more fuel when im under 2K RPM's ( loaded ) I was getting 9 to 10 mpg with a 35' toy hauler.

Now I get 14 to 15 with the same trailer, but now I run in 4th gear ( instead or 6th @ 1800) at 2900 RPM and arround 60 to 65 MPH.

he also stated that my motor is mutch happer at thoes rpms, and my EGT's went from 13's down to 10's

This is the first time I have ever heard/read this. I will have to try this in the spring when I start towing again

I have found that towing my 8K TT at 70 to 75 I get around 9.4 mpg with cruise on. I can get 11 with cruise off.

Tried the manual mode, but with no trailer.

Found that if I was going 70 and dropped to 4th gear not moving the accelerator, my speed would increase to 74-75.

If this is the case, what would use more fuel....more rpms or pushing on the accelerator more?

i would be happy with 11 or 12

I don't think it is reasonable to expect 11 or 12 mpg while pulling a 25 foot 5,000 trailer at 65 - 75 mph. Sure, that would be great, however I think the speed is the deciding factor. Try 55 mph and your goal is within reach.

Typed on my Kids I pod Touch.

Going CA to Co, 1200 miles at 60mph got 11.5 to 12.5 with 19,000 lbs (gvwr). Thats with a 5,500 lb or more truck camper and a 5,500 lb or more boat behind it. Not very good aerodynamics, but 11.5 isn't bad. Esp considering I have 10 wheels rolling along. I do my best to keep the RPM as low as possible. I found my trucks sweet spot to be 62 though. I also hit 60 in drive, then switch to t/h to get into sixth. It just doesn't like to hit 6th at 6o while in t/h mode.

My diesel mechanoc told me to NEVER tow ANYTHING below 2000 RPM
after chating with him for a while, I learned that My 06 duramax consumes more fuel when im under 2K RPM's ( loaded ) I was getting 9 to 10 mpg with a 35' toy hauler.

Now I get 14 to 15 with the same trailer, but now I run in 4th gear ( instead or 6th @ 1800) at 2900 RPM and arround 60 to 65 MPH.

he also stated that my motor is mutch happer at thoes rpms, and my EGT's went from 13's down to 10's


This could be a very true statment. If while towing, the motor stays in the RPM's with the most torque it should take less throttle to accomplish the same task (I.E. pulling hills or maintaining the same speed) as a higher gear with less RPM's.
The T/H mode helps do this by controlling the trans and not the throttle.

The same occurs when we add programmers. More power equals less throttle to reach the same goal as stock. I would think lugging the engine would use more fuel than higher RPM's and less throttle since the RPM's are dictated by the gear selected and not the throttle position.

If this theory is correct, this would only be true when towing as we are looking for the most torque and not horsepower.
Any thoughts?

I know in my semis that each truck varies at which speed is most efficient. The two with Detroits get the best mileage around 55-60 while the one with a Cummins mileage drops when speed falls below 60 or goes above 70. The funny thing is that the Cummins has higher horsepower and torque (525/1850), and shorter gears (3.90s) while the detroits have taller gears (3.50) and less power (430/1650) in more aerodynamic trucks, yet the Cummins get better fuel mileage than one of the detroits. A lot of it is about driving style and having the engine be at its optimum rpm. Overdrive will is less efficient at transmitting power than direct drive. The only advantage in over drive is lower rpm at any given speed.

Very interesting! I'm doing 12-14 with a fifth wheel towing in 6th (60-65), but I find it very suprising that a diesel likes a higher RPM, especially since I think that is well above max torque (if I remember correctly).

I am with you, this sounds about 1,000 rpm too high for the dmax lbz engine. It does sound reasonable for a gasser though.

Typed on my kids Ipod.

The numbers you give do seem low.
I'm getting 13.6-14.2 towing a Rockwood TT, it's light, but a box on wheels so lots of wind resistance. I usually run about 65 on cruise tow/haul on.
If your running the 285/75/16 tires your odometer is probably off some so your not getting correct mileage to figure your MPG. Just a guess.

I've never gotten near 10 mpg with my 97 3/4 ton 4x4 with 350 engine and 6-speed manual transmission carrying approx 7000 pounds. 7 was about the norm for that rig. Now I can pull the same load at about 14-15mpg with my 06LBZ. Empty, I could only get about 14 highway, and now I get 20-22 in summer with my LBZ.
I have done it for the last four years towing back a forth from CT to FL approx 1500 miles each way. I am pulling with a 2000 ext cab 4x4 5.3 with 3.7 rear. I know another person with a 2004 5.3/3.7 pulling a 7,000 LB 24 fT fiver getting the same results . The truck gets me over 19 on the same trip not pulling the trailer with the Hot Rod.

i tow a 27' v-nose that is around the same loaded maybe more, and get around 11.5 with winter blend and cold temps.

Just in case anyone didn't know, to see what gear your tranny is in, pull it down to Manual mode, and the number selected is the gear you are in.