I have a 2005 379X 244 wb with a MSX C15 acert 875,000 miles. 18sp 3.36 11R22.5. I pull a dry bulk loaed one way grossing 140000 lbs. I had it into the local cat dealer and the ecm flashed from 475 to 550 i think it was , it is an 1850 tq. I am getting anywhere from 3.6 to 4.5 is this normal , and how & can I improve the MPG .
Is your loaded mileage 4.5 or your round trip mileage 4.5. If it is the loaded I would say that is fine mileage and nothing to complain about. I get that with my 2012 Macks with a MP8 and mDrive when I am loaded. Round trip summer mileage was around 5.5. I can't remember my winter mileage off the top of my head.
i get 4.6 pulling 102k. 09 pete but the motor is an 07 isx 475. mileage seems to have come up a little with the summer blend now. so not sure on the new nyumber yet. last week it was 4.9 i'm about 5.8 with a normal 80lk. before it was about 5.3
get your ecm tuned, not by cat, go to pittsburg power or pdi have it turned up to 576 hp (I think thats what Bruce told Me) this is where it gets the best fuel economy. check your fuel pressure, it should be at least 95 psi at 1500 rpm. and check and see if you are getting air in your fuel. these are the best way to get better fuel economy out of a cat... I own 3, 1 gets 5.8 to 6.2, one gets 6.8 and the other ranges from 6.2 to 7.0. there are other things you can do for better economy, talk to bruce at pittsburg power, he is seeing 7-8 out of the cats
anytime your pulling heavy, you can expect lower economy. todays local construction trucks pull that much. and they are city driving. they're only averaging 3 mpg.
It isn't something I would worry about too much. If you can get it up it always helps. Before I purchased I was aiming to get 5 mpg.
