Please help! ISX15 poor fuel mileage

[Rawze]

(11-19-2020 )Nihalu Wrote:  Hello Folks
After checking several YouTube videos on Rawze's Channel and inspecting the truck accordingly I ended up in buying a 2016 Peterbilt 389 with a Cummins ISX 15 engine in it ESN 79854924. Its a 550 HP/2050 TORQUE WITH 3.73 GEARS ON 11R22.5.ENGINE HAS BEEN OVERHAULED AT KENWORTH in my area 138K KMS ago with new rebuild kit and new cyl head. Current odo is 908000 km.Everything is just fine with it except fuel mileage. Just to mention it used to run in mountains with 140k lbs gross. Now I run vans/reefers with 80k gross. Max I got out of it is 5.8 MPG. All stock after treatment.Recently changed IMAP, DELTA P AND other recommended sensors. Dpf doc all cleaned but no mileage improvement. Please help me if you have any suggestions. Call/text 7788358132.
Any help from legends around here will be really appreciated.

Thank you so much

so you buy a fuel pig of a truck with a front end that looks like a 4x8 sheet of ply-wood facing the wind .. and then you go and haul low-rent freight with it (dry-box/reefer) -- don;t comlain about fuel mileage in that pig of a truck made for a museum.. they should be outlawed in that market. - Sell it and buy something competitive (prostar or cascadia w. ISX and spec'd right for the job) in profitability and start over .. that is my advice.

Best you can hope for is high 6's in that pig... it ain't no truck for the low-rent market your in... and you buying it, either you knew this already or you did not do your homework at all towards a solid business model that actually involved profit over that antique-roadshow looks.

5.8 sounds about right if your pushing that pig down the roads at 70+ like a complete fool. - Start driving by your boost gauge, keeping it under 20 at all times, and drop the speed to about 60 of you even want to stand a chance with it in the market your in.. refuse any load that required more than 600 miles in a single driving shift so that you can keep the speeds down and the profatability somewhat in check.