Truck has 65K 325hp AT, on it, It's like 200 miles one way, & hardly any real hills to claim the trip did have a little wind to work with but nothing claimable,, Oregon city to Penelton OR 6.6 MPG and we had >0< left on the miles to go 3 mile prior, on the way into penelton,,, ohh and on the way back 5.3 MPG, filled up in Penelton and had to refill in Cascade locks. = no chip 295's w/ 5" exhaust and open air intake (calculated). The trip meter said 7.5-8 mpg.

Truck blows no smoke, >>>>>>ok I can see a, givin the open style air filer that I am changing back to stock (as is needs cleaned at least every other trip and it is completely dirty again.

I ran in tow mode for the whole trip, within 300 RPM off the rev limiter at 66MPH, change it to non tow mode and it was like 1700RPM= not enough RPM to run 66mph w/o over heating the EGT's or the trans.
This 3500 seems to be made to run at 50 in tow mode = 2100 RPM (no thanks), oh well guess it is what it is.

I added the BD in tow mode when I got home (trying to save the trans for once w/o the chip (during the trip/'s)) to compare and picked up 1.0-2.0 MPG w/o the overdrive, on the over head. But to get any better I cant afford to kill another torque converter or overdrive.

oh yeah 9700Lb truck single rear axle), and the 2 axle bumper pull heavy nose 8800Lb trailer
FYI

Might have to edit this post but it looks right so far on the little screen.

just a reference to work with, the truck runs great just a little spendy to drive

any ideas what we are doing wrong??

 

What year of truck and configuration?

First thing that comes to mind is uphill all the way to Pendelton into a head wind all the time. Yeah, there is no way to make good mileage on that route unless you draft a semi.

Still thats baaaaadddd mpg! What was your total weight? I suspect you may have a slipping TC or direct clutches under a load. Mine did the same thing and dropped lots of mpg when the trans was getting eady to go.

 

With the truck in my signature I can get about 10.5 to 11 mpg cruising 65 mph towing the 5th wheel that's also in my sig. What gears are you running? You mentioned not affording to kill another TC or OD, have you done this before? When did you first start noticing the poor mileage?

 

Before you say that you had better do that exact run and see what happens.

I can get 11-12 mpg grossing 23k with a big square nosed GN trailer in lots of places. I get 9-9.5 on that run with just about any decent weight and trailer. Thats a tough pull up the gorge into a constant headwind.

 

you're right, I do see a drop in the mpg's when I'm in the hills, so 9 mpg at that speed doesn't seem too bad. Wonder what a gasser would be doing?

 

I did that same trip yesterday and only got 16.5mpg unloaded at 70mph with the AC on. The windmills were spinning and it is all uphill. I thought mine would have been better as well. I even removed the front drive shaft for the trip!

From Troutdale to The Dalles, I was able to run without AC and was sheltered from the wind running 65mph and was seeing 20.2mpg.

 

Oh, about 6-7.

Been there , done that with a 440 powered dodge and a 350 powered GM. Its all bad on that run.

 

Yep, right at what I got all the time. No matter how I drove.

The lower end is better but from the Dalles to Hermiston its wide open and ALWAYS whitecaps on the river. The upper end is one huge funnel.

 

No kidding. Made the trip home today and the overhead said 19mpg at 70mph even with the AC on. I am in a six speed manual no less!

It had been a while since I had been that way during the day and I was surprised to see all the windmills. You never realize how big those windmills are until you drive by a semi with one blade in tow!

 

thank you for the inputs!

You guys normally run in tow mode the whole time?
We did have the AC on and cruse set and I checked it has 3:73's

 

that terrible mpg. I would get that coming through the mountains from Glamis to San Diego pulling a LOADED toyhauler.

 

you are not going to like what it cost to to get better mpg from a 04.5 to 07.4's. to minimize the in cylinder egr system along with the needed upgrade to the at, you need to keep the truck for a long long time. return the air back to stock, replace the cam to pdr, replace the nozzles with 50hp ddp, get a smarty jr. all three work together, and will reduce egt about 300* and gain 2.2 mpg loaded 4.5 mpg empty. take the truck to bd and do the complete kit to the automatic transmission and have them install the bd exhaust brake at the same time