I just returned from a trip with my 2004.5 LLY CrewCab Dually (2-wd).
Drove 2,228 mi. RT from Oak Harbor, WA to Rangely, CO.
This THING managed to somehow guzzle 129 gal. of fuel netting me only 18.04 mpg with an avg. speed of a measley 64 mph!! AND the truck was empty!

Totally unacceptable! I had expected it to get at least 20 something over the road.

I mean...I realize the truck is totaly stock (except for the EGR Block and a couple of extra holes in the Air filter box) but I get 21ish mpg's traveling to Tacoma and back so I expected roughly that much on this trip.

I gotta find me some inexpensive mods to do to this or I'll have to sell because 18 is no gonna cut it!

I was thinking about maybe puting in a super chip or something like that to up the HP by maybe 100 hp or so. That might help keep the rpms down to a reasonable level (1650 - 1700?) to up the mpg's.

I'm open to other suggestions though.
Terry B.

 

so many things that can influence MPG. wind, hills, tire pressure, temperature, etc. your cat may be loading up with soot causing more exhaust back pressure hurting mileage

a tuner can help but make sure everything else is up to snuff before turning up your hp

 

Yes those thins will definitely have an influence. @ 50,000 mi. I can't imagine the Cat loading up (although it may be possible but then I wouldn't be getting that mpg on the shorter Highway trips). Engine temps have never risen over 210 yet according to the gauge. and I keep the tires aired and rotated.
Like I said..I am gettng over 20 during my shorter trips to Seattle and Tacoma. If any of the above would be wrong I would think the MPG's would be lower all the time.
Yup...a lot of hills between Seattle ad Rangely CO. and that might have done it..not sure.

Thanks for the reply,
Terry B.

 

hills will kill your mileage pretty quickly

18 really isn't that bad for a truck that weighs 6000lbs+

the biggest gain I saw in mileage was when I added tuning, I run EFI live with tunes from DURAMAXTUNER.COM | Custom Duramax Calibrations. DSP5 ECM's | SPADE Series | EFILive, and i get 20+mpg on most long trips, just depends on my speed and driving style and the terrain

what truck would you go with to get better mileage? and keep the comfort and power of your LLY?

isn't there a pretty significant increase in elevation between washington and colorado? the thinner air will affect mileage as well to a small amount, as well as the extra effort required to climb those grades

 

What truck for mpg AND comfort???

I think most likely an '06 Dodge Cummins. My Son-in-law has one and he's getting 25-217 over the road on hs trips from Seattle to Phoenix (several a year) and it's very comfy the way he's set up.

But if I had to choose a truck I already own it would be my '93 dodge Cummins. To increase the comfort level I think I'd change out the seats with her Chevy (if they'd fit). They are very comfy plus I likethe heated seats feature! I'm not sure if a set of seats from a newer dodge would fit in there either though.

I think I'm going to try to get me a programmer and up the HP by about 100. I THINK (i really don't know much about it) the HP increase would result in less rpm's to go the same speed and that's where I'd see my mpg gain.

Terry B

 

The hp increase would only reduce RPMs if you don't now have enough power to sustain
OD or high gear, and you would with extra power. Otherwise RPMs will be the same

 

2x

it will also cause it to shift to the next higher gear a little earlier. with the increase in hp, less throttle will be needed to develop speed. at less throttle the transmission will shift up sooner, thus running at lower rpm till your up to speed. this + the usual increase in timing is where the extra mpgs come from. when at a steady speed and rpm, timing and fuel pressure are the only thing at can help. that is why most of the benefits are at city driving & minimal at highway

 

there is no way your SIL is getting 25mpg true with is dodge, I had an 05 and the best it would do tuned is 21, and the ride and comfort were inferior to my Chev

 

Turns out my SIL's truck is an '05 Dodge and he IS getting the MPG's I stated in my previous post...
I personally calculated them on a recent trip with him.

Oh...and I get similar numbers with my '93 dodge.

Both trucks are 2-wd long beds. His is a crewcab while mine is just the clubcab.

Personally I'd drive my dodge everyplace but the wife refuses to ride in it as the noisy Cummins gives her headaches so I have no choice but to drive her DMX.

Terry