2012 DD15 fuel mileage

Hey guys. I’ve been on here quite a bit lately and read a lot about my problem already, just wondering if there’s any other in site.
I recently bought a 2012 Cascadia with DD15. Problem is it’s only getting about 3.75 MPG, average between loaded and empty miles which are 50/50 split. Here’s the specs.
-46,000 rears
-22.5 tires
-3.91 gears
-Eaton 18 speed
-550hp DD15
-46,500kg loads
It has been -40 Celsius here for the past week which is as long as I’ve ran the truck.
It has been doing the “rak rak rak” while
Idling so I’ve purchased a new fuel quantity valve. Do you think this will help the fuel mileage? Anything else I can try? Or is this just normal? TIA

 

I did idle a couple of nights. But those MPG were based off of running time only. Doing a load of 2 consecutive loads and filling up and figuring it out! Fuel is no different than any of the other guys I work with.

 

Better than 3.75... I’m not looking to go broke. Guys I’m running with on the exact same run burn upwards of 200L less in fuel per day. Same spec trucks. Yes I know there’s 1000’s of differences and things that can cause crappy mileage. Just was looking for maybe something obvious I should be checking. I will get the trucks boost system checked for leaks on next days off! Thanks