14 Mack, 4.6 mpg? Can I get better mileage with it?

Maybe if I was lighter, I'm loaded to 79.5-80k all the time unless I'm empty. My foot isn't light either

 

At 62 MPH my 2012 VNL64T780 DD 2.64 D13 1350 RPM 80K lbs was consistently doing 8.25 MPG US.
From AB to IL via MT. Reefer loads, no rush, West winds from behind, slightly going downhill all the time.
Going 70MPH on same route MPG dropped to 7.25 on average.
MT was 55MPH from Shelby MT to ND border, in the night time, though.

 

Lotta flat land there lol the roads I run in PA WV and VA are the exact opposite of flat

 

The worst fuel mileage I had was in UT driving at 89 MPH fully loaded. For a short time only, of course.
5 MPG.

 

Right. The Appalachians will straight punish a heavy truck.

 

OK I meant the Mack dealer but you answered what is causing the problem, the delete.

 

Because tires and aerodynamics aren't costing you 3 mpg. I have a ragged out ISX with 991k on the clock. 1,500 rpm at 70 mph, I drive like a dick head with my foot to the floor wherever I go, and I get 1.5 mpg better than you. Heavy, light, flat, mountains...the only times I ever get lower than 5 mpg on a tank is when an unlucky 34 reset has me idling for 60 hours over the weekend.

It's the tune that's causing it, or injectors, or something else, but it's the engine that's the problem.

 

Just for clarification, it should be getting better fuel mileage with the delete, but some people should not be allowed to write tunes at all.

You need to be looking at what's wrong with the engine. Do some research and find a reputable tuner. Your engine is pouring diesel into the cylinders. Much more than it should be.

What's your cruising boost at 70 on flat ground?