I am running an 04 pete 379.

Specs
MBN 24234 C15 ?475?
rtlo12913a Transmission
3.36 ratio
295/75 R 22.5 rubber

68 mph= a tad over 1400 rpm

Company governed the truck down to 68 mph

Average milage on my calculator is about 4.3 to 4.6

I pull a 45 foot Trinity Eagle Bridge 3 axle belt bottom with a dome on the top to keep the potatoes from freezing in the winter. Average empty weight with half a load of fuel is 34,500 lbs.

Average gross weight is 88,000 to 96,000 depending on which roads I am running. I have a 10% over permit for state roads so I run 96,000 on them.

They had the over head done on it just last week but it did not seem to help.


We get a fuel bonus for averaging over 5 mpg. My old truck a 01 Volvo 670 with a VED 12 465 and a 10 speed used to pull the loads much better and average about 5.8 mpg and that was at speeds of over 72 mph alot of the time.

I don't idle the truck unless it is for cool down from coming off the highway. It has a Tripac on it for heating and cooling if needed but I try not to run it unless it is absolutely needed due to extreme temps to keep from sweating my butt off or freezing up solid.

North Dakota does not have many hills but we do have some out in the western part of the state and I have alot of trouble getting up these hills. I am down to 25 mph coming out of the Painted Canyon (Medora) were others with the same motors and final gearing can pull them at 40+ mph.

Please help. This rig should beable to average over 5 for the most part.

My boss is not big on spending big bucks but I am willing to spend a little myself if I can start getting a fuel bonus again and beable to pull hills.

Mind you I am not rich by any means so please keep that in mind.

You said it all, 379 (like pushing a shoe box), grossing 96,000 (heavy and pushing a shoe box). I'd say you are lucky to get what you are.

You have to spend money to save money.
I was the same 4.3 now at 5.6 as well as a lot of other problems fixed and thats running at 110,0000 with 4.3 rears.
550 will have a few ideas might be able to help.

Re-check the # on your trans.with a 475HP you shoulg have a least a 16913 trans. Also those 336's are not helping you with the size of load you pull. As far as the "boxy" hood well, I do pretty good with mine even though mine is a classic W/Cat (Acert) 16210b trans,and 3:70's, 22.5 tires. Keeping my RPM's at 1500 (65MPH) getting 6.75 MPG's.The one thing that did help mine was the power harnesses from Platinum performance , using both bumped up my HP and fuel mileage by 1/2 MPG. Hope this help's!! (Kinda wish I could trade rear ratio's with you)

the truck isn't the problem it's that MBN

It is the MBN, its a bridge motor. Some run good some run like shiet. I bet the catalytic converters are plugged up, i would get rid of the stock mufflers at first as they have the cats in em. The biggest issue here is the ecm, the MBN ecm needs to go for a 6NZ C15 ecm. Untill you do that nothing can be done to it other than muffler change, you can put a fuel temp wire on it, it will bump power 50hp and give you some good mpg gain, i saw .5mpg increase with one. They go for $80 if i remember.

Mine was a 525hp MBN and ran like a raped ape, with fuel temp wire for some reason i put 625 acerts to shame, it did 517hp to the wheels in bone stock trim, with the wire im sure was doing 550hp to the tires. It did get 3.8mpg at first though LOL.

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LOAD EM LIKE RAIL CARS, DRIVE EM LIKE RACE CARS!!!!

I got all the information off the tags in the glove box and other places on the truck.

Well the door tag called for 11R 24 rubber but that is not what it has on it.

I do know that in top gear at 68.8 mph I am turning just over 1400 rpm.

I usually shift at about 1400 rpm and not let it dip below 1200 rpm but with these loads I can't get the thing moving unless I shift at 1500 to 1600 rpm and forget about hills of any kind at less then 1700 rpm.

Most the time I leave it in the bottom of the top hole when loaded or bucking a wind in slight hills. If not then it seems to be working so hard and not going anywere.

I know Cat had it hooked up and they said I was getting 5.5 according to the computer but we all know that is false. Nothing beats going by actual fuel used at the end of the day.

But the serial number for the truck is 1XP5DB9X74D821891.

Butler Cat in Grand Forks ND just did the over head on it and updated the computer or something. They said that everything is as it should be as far as boost, FP etc.

I heard something about fuel filters making a difference. The company uses Baldwins. Will swamping out the filters possibly help?

You just need to stop giving advice on trucks and go drive a vulva.

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LOAD EM LIKE RAIL CARS, DRIVE EM LIKE RACE CARS!!!!

Well you shouldnt lug it, the MBN is not like a newer acert and needs to be ran at 1400+rpm, rev it up to 1700rpm and split but dont lug it down to 1200rpm.

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LOAD EM LIKE RAIL CARS, DRIVE EM LIKE RACE CARS!!!!

the 475 MBN I had in a t800 KW got exactly the same fuel mileage you are reporting Rat. and it didn't matter if I was running 55 or 75.... well okay, 75 in the mountains out west it did drop below 4mpg a few times