500hp n14 mpg?

details please

Rear end ratio

Transmission

How hard are you driving it (mph)

how clean are your filters?

 

First check mileage the old fashion way, not with the dash readout. Check the CAC for leaks, clean air filters,set overhead , check mufflers some can become very restrictive.

 

Weight and speed are two of the most determining factors.
i.e., 10,000# in my reefer at 60mph and I'm around 11 mpg.
Same trailer, same truck, same route, with 40,000# in the box and I'm around 7.5mpg.
If I increase speed, my mpg goes down. If I'm in a head wind (or tail wind) mileage changes.
And where you run makes a difference. Mountains, plains, etc.

 

Unless you pull oversize or really heavy there is definitely something wrong. Probably a boost leak. A friend of mine with the same engine pulling a tanker in a W900 gets 5.8.

 

I have a 460 hp n14 I pull flatbed and she gets 6-7 mpg running 65 - 75 mph range. Try putting lucas in your tank, it help me out a little.

 

Wow...4mpg?? Check gallons against miles, do a little math.

I've got an N14 @ 525hp and the lowest I've gotten is 5.4, highest has been 8...mid-6 to 7 is more typical.

But I'm not OTR....daycab, local, short dump trailer usually grossing 73,000...lots of stopping and going...in the relatively flat lands of northern Illinois.

 

I used to have a 98 international 9300 it was 525, 13 speed and 3.73 ratio hauling dry van always around 23-35k lbs hauling milwaukee to southern texas miami and back up he averaged 6.2 to 7.3 but never below 6.

 

11 mpg? What are you running?