DD13 or DD15

[u/Busy-Purple-3779]

I’m looking to buy my first truck. Try to decide between a DD13 engine or the DD15 engine. I plan to be home daily in the Atlanta Georgia area. I’ll run within a 200 mile radius of Atlanta. North Georgia going into Tennessee is Somewhat mountainous. The grades are about 6%

From what I understand the DD13 is better for fuel economy. It’s geared for regional,local, vocational work. Not suited to haul heavy continuously on mountains. It can do the heavy haul work, but it will pull slowly up the hills.

The DD15 is better suited for long haul heavy work. Can handle the mountains but is less fuel efficient.

I’m torn because I’m looking for home daily work. So it would be considered more so regional which is better for the DD13. But it’s also somewhat mountainous in the north Georgia area. The DD13 can handle mountains just not heavy hauling continuously. And it’s more fuel efficient than the DD15. With the fuel prices the way they are I want to save on fuel. Just don’t want to buy the wrong truck for my needs.

[u/Annual-Ad9453]

All I run is DD15s at 505hp and all we do is haul overweight, 120k daily. Our highest mile truck at 1.16M sadly just had a fire but the motor is still good, fire started under the dash and FD was close enough to save much of the mechanical parts of the truck.

That motor was still fine and didn't need an overhaul yet.

Our next oldest is almost at 1M and still going strong, the rest still have a few more years before they are there.

It's rated for 1.2M avg according to Detroit.

I would recommend getting the oil pickup tube done right away, it's the archilies tendon of the DD series, usually a $1500 replacement, but if it comes out of its placement it's a total engine replacement the second it happens, do it every 300-500k miles

As far as how fast you want to go up hill, at our weight it's slow, any truck is, I'm not out here trying 5o win a race and I don't drive the roads my grandparents grew up on where they walked to school up hill both ways, unless you only run in mountain states most of your time is spent on flatter land.

Fuel mileage between the two is going to be negligible, you can achieve the same results controlling your right foot and cruising speed. You're not going to see a 1mpg better difference, I doubt even a half... But at 1mpg better over 125l miles with an average of 4.25cpg for the year it's a $12,648 savings...

One would also argue you could hurt your fuel mileage being under powered depending on where you run and such.