Terrible gas mileage on 12' T700...

did you check for codes. most of the newer trucks have a way you can check code on the screen without having to plug a computer into it. could be a ecm problem or some sensor that's causing the computer to make changes to the fuel system. If you have a leak in the cold air intake, that will also create mileage loss. but there will also be a power loss. how long have you had the truck? maybe there is a power loss and you just don't know it.

 

Have the cold air checked. what I did was I bought a cheep fog machine. took the filter out and put the fog machine near the air breather. ran the motor at high idle and let the system draw the fog in. if there's any leaks you will see the fog seep from the areas. how are you checking the mileage? are you reading what the computer says or doing it by how much fuel you are using divided by mieage. don't trust what the computer says.

 

High exhaust temp may actually be a clue. Perhaps the DPF filter or the doc face is getting plugged, the EGR system maybe getting plugged, etc.

 

it's a 2012. that should be DEF.

 

Switch to diesel fuel too , just kidding ya lol

 

Thanks for tolerating my sence of humor ...let us know what you find out !