Well I'm sure the Megcab weight is heavier then the SB Ford's weight so that will effect your mileage some. Also you said the Dodge sits up higher then the Ford so with it being up higher it will have more wind drag then the Ford that sits lower to the ground. How wide are the tires of each truck? A wider tire will lower mpg over a skinnier one and IIRC a 17 inch tire takes more power to turn over then a 16 inch tire.

 

There is no way that a megacab is heavier. It's teh other way around.

 

Now I realize that I have a second gen (possibly the greatest trucks ever made ) but this weekend I had to make four, 60-mile trips that are nothing but hills and curves pulling a horse trailer that weighs probably 6500lbs and i was hard in the throttle running 70-80 the whole way and i checked the mileage and still averaged 15.4

 

Your Dodge truck is set up for empty mileage over towing mileage with the 3.73 rear end. You should get better towing mileage with 4.11. With your description of the towing, are you hand calculating the mileage or are you using the overhead?

 

My gasoline powered pickups with high differential gear ratios are used as runabouts, while my diesel truck is used for work. Nevertheless, I also like to have a higher differential gear ratio in my diesel work truck, because it happens that I pull a higher percentage of light to medium weight loads than very heavy loads. A lower axle ratio would be in order if my truck always pulled 20k pounds or more most of the time. A manual transmission in 6th gear and a 3.73 axle ration has a slightly lower final gear ratio compared to an automatic transmission in OD and a 3.73 axle ratio. When I pull a heavy to moderate load I travel at a lower velocity, 50 to 55 mph, and down shift the tanny more often on inclines which is fine with me. When I pull a light load I still do not like traveling faster than 60 mph in case something goes wrong.

At 60 mph with a light tail wind during the day time I pulled an empty 3k flat deck tag trailer about 300 miles and I hand calculated 19.6 mpg. At 55 mpg at night in dead calm air with 10k pounds total payload (trailer and cargo) on the return trip my hand calculated mileage was 18.5 mpg. Traffic was extremely light during the day and almost non-existant at night, so I used the cruise control 90% of the driving time. The four lane highway was fairly smooth and the truck ran perfectly. I feel the higher 3.73 rear ratio is right for my CTD that has lots of power.

 

I'm in the same boat as you. I go from central Pa to In. on I-80 to pick-up campers. I was getting 12 mpg on the way out empty and 9 mpg on the trip home with a 15k high profile 5er. Was driving 70 mph both ways. Truck is 06 drw quadcab with 4x4 and the 6 speed with 15k on the clock. Its and amazing puller but sucks when it comes to fuel mileage. 2 duramaxs went with and got 18 mpg out and 12 in with a fuel cost of $100 less. Whats up with that?

 

wrm your not driving it hard enought. drive it like you stole it .

 

flyright, you should put more specifications about your truck in your signature, like whether your rear end ratio is 3.73 or 4.10 etc. Do you know what the differential ratios were in the Duramax equipped trucks? You have to realize that high ground velocity creates much air drag resulting in excessive fuel consumption, plus high engine rpms gobble fuel for an I-6 long stroke engine designed to operate more efficiently at around 18k rpm.

All I know is that I can get fantastic mileage if I drive at the speed limit when empty or when there is a tail wind, and under the speed limit with a load especially if it has a large frontal area.

 

his choices would be 3.73, 3.73, and some dmax's could be special ordered with 3.73's.

 

Now the real question is...........




















Can you get a Dmax with 3.73 gears???????

 

My two cents:

1) The Dodge auto vs. the Ford auto - Dodge = 4 gears, Ford = 5 gears

2) Number of miles on the rig. Personally I didn't really get a mileage increase and start to feel that the engine was broken in on my truck until about 28K miles. Of course that's because I rarely tow anything and it took a long time to break in.

3) Like mentioned before, drive the snot out of it once in a while and it'll help loosen things up. Talking to a Cummins mechanic one time I asked him about the break in procedure - he told me to go load up the truck bed and hook up a heavy trailer and go drive the snot out of the truck for about 200-300 miles - using as many hills as possible. Since I don't have any heavy trailers at my disposal, I just try to drive the snot out of it empty a bit more often.

 

My truck has the 3.73 gears as did the dmax's also.

 

I drive the snot out of my truck every day. I pull 14-16k everywhere up and down hills fast and slow. This truck sucks on fuel mileage. Towing or empty. My 03 was sooooo nice in comparison. It did have 3.73 and much lower output. I have to drive 55-60 to see 17 empty. I don't dare hand calc while towing. But at the end of the day it pulls like i wan't it to, really well.