2018 Pete 389 with Cummins X15

That's about normal Ha Ha!

Watch the idling if you plan on keeping the truck for more than three years. The soot will tear that motor apart in short order, and the cans. The SCR system too, when they get the volcano going in the plumbing, which you eventually will, really need to keep an eye on the emissions. Then the fuel pump, with all of that idling, I would rebuild that pump annually, make it a regular maintenance item.

 

Not hauling heavy, but normal freight 7-8 mpg is easy to get with a hood. You just need to know how to drive it and rid yourself of the mandate. There are guys doing that today with them. Keep your foot out of it, drive with your boost gauge and turn off the cruise. Give it a try. Keep boost under 15 at all times, that is where your fuel goes.

 

my w900 2016 isx15 18spd. 3.55 rear only gives me 5.6?? well i do use cruise control i set it at 65. any help ??

 

Drive with your boost gauge, I have a friend getting 8 mpg with his W900 with a Cummins CM-870. Another with the CM-871 in his dump truck, always heavy working local, he is over 8 mpg. They both had their trucks tuned by Gearhead over in Oxford PA, his shop is next door from the Flying J. Price's Diesel Repair. Haggai Automotive and Diesel in Griffin GA also, he is one of the best around if you are ever down near Atlanta.

I don't see any reason why you cannot do the same, most likely the emissions are what is killing you, unless you are say heavy haul or pulling something odd ball, or idling, which is not good for these EPA motors, kills them quickly.

Also, keep an eye on your fuel pump too, you have the CM-2350, and when they go they go. If you catch that in time, usually it will throw a fueling code, shut the truck down immediately. The base price to clean out the shrapnel from the motor is around $10,000 and there is no guarantee they will get it all. The worse case is that you take out the block, then you just weld a hook to the top of it and send it to the marina for use as a boat anchor. If you do not know about the fuel pump, you need to seriously look into that. It should be a regular maintenance item. They tend to blow apart between 200,000 and 400,000 miles. I would rebuild say every 18 months to be on the safe side.

Also, DO NOT lug that motor! They are prone to liner fretting! #5 cylinder/liner seems to be the one that likes to cut lose. Run the RPM's high, none of this 1250 RPM stuff, especially when pulling a grade. You fret a liner you are looking at an in frame.

Good luck! And happy motoring!

 

Previous company I worked for, all their cm2350 and x15 with 10 speed ultrashift small step drive (.80 to 1 on 10th gear paired with 2.64 for tandems and 2.67 for singles) They drive em between 1150-1200 rpm at 65 mph. They will destroy em.

 

Thanks for the advice, that's usually what I pull it down to is 1200 then split gears. Maybe I'll start splitting a bit sooner.

 

Previous truck was a 386 with the ISX doing the same work. Only issue I ever had was the NOX sensors needed replacing about every 18 months. Was around 20,000 hours and 450,000 miles when I gave that company truck back and bought my 388. The key to keeping these emission trucks alive is drive them like you stole them. Keep the scr/dpf hot hot hot and it will do its job properly. If you baby them they will give you lots of problems.

 

Do not lug these motors. 1650 rpm’s seems to be the sweet spot for the best fuel economy. Progressive shifting these motors like you would an ACERT Cat is not recommended. Engine damage can occur. Liners are their week spot. The #5 and 6 cylinder liners tend to fail, very common issue.

 

1650??
Mine sounds like it's going to blow apart that high.
I did drive it that fast for an extended period last week however. Cruise on 75 for 2 days. I did actually get better than expected mpg. However I was slightly lighter, 75000 maybe, and there was little to no wind, which is rare.
I generally keep it in the 1400-1500 range.