i still maintain that the kind off milelage you say you get is the exception not the norm.
i "baby" my trucks, overkill on the maintence, use synthetics front to rear
everyday driving on pretty much flat ground at 55-60 mph, i will stay in the 14-15 1/2 mpg range.
I still remember my grandpa telling me before i was old enough to drive "always accelerate as tho you have an egg between your foot and the accelerator and be careful not to break the egg. Do the same when you are braking leaving lots of "cruising time " between deacceleration and applying the brakes.
That is pretty much the way i drive. Hard to Imagine that out of four trucks (2 2nd generations and two 3rd generations) that i haven't been able to get one of the 20 mpg trucks

 

See signature.

 

Saw 17.4 as the BEST if driving REAL(pain in the butt easy) easy and never over 60 non towing.Usually I'm in the 14 to 15 range.Towing 10k is 12 tops under 70.

 

my truck can't get more than 13mpg empty.I had the dealer reflash it the overhead said 14mpg when I picked it up and by the time I got home the overhead said 12.8 all freeway empty doing the speed limit

 

And the speed limit was??? 70? with 4.10s.Try resetting overhead and keep RPM's below 2grand.Anything over 2 grand and mileage falls to heck with all of them.

 

I'm seeing an improvment with more miles. Now at 15k + and am getting between 15-16 around town, Took a trip with the wife and mom-in-law to Cripple Creek and back to Denver and hand calc. was 20.65.
I think with more miles you'll see an improvment.

 

My '05 is still relatively new to me, but this past weekend I towed from Melbourne to Jacksonville, FL, then to Valdosta, GA and part of the way back before stopping for fuel. Hand calculated was just over 15mpg (around 15.2 I think). My little 6x10 enclosed trailer is probably around ~2700lbs or so loaded with two bikes in it. Truck is stock other than a Quad box set on 30hp for towing.

 

your truck is not broken in yet my 05 just turned 10000 miles and is finally getTING alot better milage , towing my 11,000 pd fifth wheel i get around 10 miles a gaLLON

 

Herb.....we have the same truck except I have a G56....I have been getting 17 City/Hwy and 14-15 with 14k behind it......when was your truck built?

 

I average over 20 on every tank that I run empty. Last fillup was 378miles 18.5 gallons. 21.4mpg. This is mostly rural hiway miles running 60mph but with lots of hills. Many thounsands of feet of altitude gained and lost on this tank.
I am sure that I could get it down to 19mpg with a few full throttle passes or by running at 70mph. On a 3000 mile trip with the cabover camper (over 11K gvw) we averaged 15.2mpg. And yes it does drive my wife nuts that I record fuel consumed and miles ran so I can hand calculate my mileage.

My truck may be a little more efficent than others but I think it is mostly the driver.

Regards,
Jim b

 

so is there anything to do that would actually help fuel mileage out at all??

speed limit is 65, we go 70 towing max, usually 65-70. the truck never seems to be straining at all, except going up a big grade it will downshift to 3rd.

 

no one here is considering how much 4.10 gears will kill mileage compared to 3.73s ....

 

i have 373 gears---shutter to think what the 4 10s would do to my milelage

 

I hand calculate every tank too. Right now I have 380 miles and my tank is still half full. I usually go over 600 miles per tank. I usually use around 31 gallons for that. No additives. This tank has been driven slow and on flat fround with nothing in tow. I do think I will clear 20 mpg this tank. My overhead is reading 22.8 but certainly not accurate. That is the highest I have ever seen it read. I have towed some and usually get in the 12-13 mpg depending on how fast I am towing. I have 23k on the truck now. Jim

 

I own a 04.5 Check sig and I have kinda a heavy foot. I would average less than 15 overall when I got this truck. Part of the reason is I went from a 94 with the 3:54 So I love the punch and power of the new one. If I keep of it and drive 60 on the highway I can average 18 if I am lucky. And by lucky I mean put up with the torture of going 60 on I95. But if I do 70-75 the mileage tails off to 16.8. But this only becuase I added a Racers Choice air box(230) and a Extang Cover. These will boost your mileage up right away. I plan on pulling taller tires on within a couple weeks. I am only going to go to 295/285 So the larger tire won't affect the mileage it should help it. By my math this tire should drop my ratio to about 3:90 and hopefully better fuel mileage. And before all you jump on the band wagon of larger tire-less fuel mileage. 285/295 are the same weight as a 265 so the rolling resistance would not come into play.

One other thing about these people with high fuel mileage. They have the 6 speeds and some are 2wd. Keep that in mind. So check into a bed cover. I love my extang RT (truckcandy.com-bestprice found) and the airbox lets you hear the turbo scream. I also plan on dropping my kitty cat of at a farm to live with the other kitties. So I will let you know how much that helps.