2050lbs of torque

go big or go home

 

That's right

 

The more the better, drive it right and you wont burn any more fuel.

 

Torque is what gets you up the hills.

 

I won't tell you what is going to happen, but I will tell you the differences I've noticed in a 450hp ISX and 550hp D16. I can drive the bigger engine "right", and get 7 mpg with a fair amount of bobtailing mixed in. I can drive the smaller engine full throttle up the hills and jake brake all the way down them, and I get 8 mpg while almost always loaded.

There's a reason they make smaller engines.

 

"Main concern being fuel mileage"

Then no, you need the X15e with 1850Tq@1000rpm

Performance series is much lower compression and programmed for performance not efficiency.

With the efficiency series motor you'll want different rears too, in the 2.80 - 3.08 range.

Big difference in fuel economy, minimal difference in Tq and available at much lower rpm

 

8 miles per gallon in an ISX? Doubtful. Aside from the X15 Performance model, all the new engines will get good fuel mileage. Of course it depends on gearing, load, route and driver. I fully believe the driver is the biggest factor.
I've heard really good numbers on all these engines and believe I could get good numbers with all of them pulling reefer at 75k plus gross weight.
The drivers saying torque is great are correct. That torque will get you to the top of the hill faster than the rest of us. Your fuel mileage will suffer of course. If that's how you validate yourself, then I would say go for those big hp and torque #'s.

 

The more horse and torque, the more fun it is to drive, at least that's my theory anyway.

 

I fully agree! I had chance to drive a turned up ISX 15, that truck was fun to drive.

 

My cats only 550 1850 and getting weaker it seems, needs to be cranked up to 650 or a little better.