Pete 379 with Cat C-15 mpg?

Would doing a ECM upgrade do this I'm going to set it at 550hp

 

that would help, but I think Oscar is on the right track

 

I know when I test my pickup or other pickups for air leaks I will make an adaptor and put it right on the intake of the turbo and charge it up to only about 10 PSI maybe 12. I turn off the air supply and wait and listen. I give it about 30 seconds or so and if no major difference its good. The only air that should be leaking out is through your valves in your motor which will cause a bleed down but not 30 PSI in 6 seconds. That kind of PSI going in should allow for some sort of pressure to be in the system still after a good minute!

 

It drops to around 15psi and holds it just not 30

 

How are you testing it? Do you have plugs for both sides, a gauge and shut off valve?

 

No that's not the way we did it

 

I just recently bought a 2001 Peterbilt 379exhd, 70 inch unibilt sleeper, with 3.55 rears, 18 speed, 550hp, 11R24.5 wheels, was thinking about taking it to Pittsburg Power, but just talked to a guy today and he was asking me how is my mpg, I've been checking it in the last 2 weeks since I bought it, and been getting 6.75 to 7mpg, but I don't haul heavy, on the average 15k to 20k pounds. He mentioned to take it to Antrim Diesel in Greencastle, PA, to boost the HP to 750, and he said I'll be getting like 10mpg.

What do you all think about that? Or should I just keep the original specs?

 

Don't fix what ain't broke. I agree more HP will return better millage up to a point. When you pass that threshold fuel millage takes a dive. I have seen thousands of dollars spent just trying to get the numbers you are already getting.

 

I second wore out if it ain't broke don't fix it you're doing fine with fuel milage I wouldn't mess with it

 

I'll take you advice, guess don't need to get the ECM tuned, I'm very happy with my truck, goes uphills really nice, I average around 68 mph, the jake brake holds at the medium setting at 68 mph going downhill, haven't needed to hit the brake pedal at all.

I previously owned a 2012 Kenworth T-660 studio sleeper, 455hp, 10'speed, Paccar engine, but the Peterbilt 379exhd, gets better fuel mileage and has a lot more power, I love the sound of it, thinking maybe getting the bigger exhaust pipes, to get it louder, hehe.