2015 Volvo 780 D13 Weird MPG when truck and trailer on park

He better drive down the road with the tractor brakes on instead of the trailer brakes if he wants to keep his job

 

Is it an I Shift?... If so, Is it in Neutral, or is he leaving it in Drive? Not sure if this would affect that or not but in my head it could... I think....

Also are you sure it is MPG, with tractor brakes set, or is it GPH?... Gallons per hour.

 

Volvo’s have a “constant warm” feature that when activated will keep coolant and cylinder temps up, raise oil pressure, and puts a slight load on engine by over-fueling the injectors when needed and keeps excessive soot from going downstream. This is an awesome feature because it prevents “wet-stacking” where the cylinder temps get so low that it cannot burn all the fuel injected into it at idle anymore and it washes the cylinder walls with diesel fuel and contaminates the motor oil.

There’s a few parameters that have to be met in order for this feature to activate...
-Outside temp below 50° F
-Truck has been idling for atleast 5 consecutive minutes
-Yellow tractor parking brake knob popped out and truck brakes set
-Clutch pedal cannot be depressed, so don’t rest your foot on it. (It’ll trip sensor)
-Not 100% sure on this one, but I’d say if there’s a major fault code it might lock itself out

Again, the truck brakes have to be set but you CAN leave the red knob pushed in and leave air supplied to trailer (I hardly ever set trailer brakes anyways unless unhooking)

If you pay close attention, you will be able to hear the engine change pitch and sound a little different and the oil pressure gauge will go up 10-20 psi and stay around 55-60 psi instead of 30-35 at a hot idle. Almost sounds like the air compressor, AC compressor, and massive alternator load all kicked on at the same time. You can hear turbo whistle a little bit too. Remember its gotta be below 50 and won’t do anything until first 5 minutes are up