T680paccar or evo dd15

Important thing to note is that any drive-train you will hear about will include the teething pains of the Cali-compliant exhaust systems.
Had a Pete day-cab with a PACCAR that was just a great pulling truck. I really liked driving it. Unfortunately, it kept throwing codes related to the emissions system that the dealer could never permanently fix. Switched to a Pete with an ISX. Under load, some of the regular hills I ran would require a gear lower than the PACCAR motor. Slowed my run times down a little. But, never had to leave it at the shop for a day or three. Any problems it had (not drive train related) were fixed in a few hours tops.
YMMV

 

7.7 is great MPG. If they both look good to you, and you have verified for yourself the DD motor, and heard all evil things about the PACCAR motor, why would you even try talking yourself into the PACCAR motor?

I know our wrench changes and fools around a lot with Cascadia DPF's and their components. Most of these are '13 and older, so the new ones may work better.

I've personally talked to a lot of guys that have had PACCAR & ISX engines with all kinds of WTF horror stories. That being said the newer versions the guys I've talked to seem to have far less problems.

I think how you drive a truck, and especially how much you idle, plays a HUGE factor on how that engine is going to do.

There is a guy called RAWZE that has an entire series of videos about ISX engines, and " How To ", especially concerning the EGR/DPF systems. I mention this, because the PACCAR is similar to the ISX.

Buy a Volvo and fuhget about it.

 

Had a 2016 579 Pete with a Paccar...left the company with 175k on the clock, and the only time it saw a shop was for service with 1 exception...the engine had a recall to have the cam replaced...there were several years that had a bunch of engines under that recall..I guess the heat treating on the cam from the parts manufacturer was insufficient. As far as Mpg's...before the cam replacement, summer would see 8-8.5, winter blend fuel knocked it down into the mid-high 7's pulling a reefer. After the cam 8 was best 7.3-7.8 in winter. As far as pulling, the company has us governed at 63, but if I got behind a similarly governed truck, and it was a Freightliner with a DD engine...I just waited for a hill and drove around it like I was a super trucker. I'm with another company now in a T680 with a Cummins..7-7.5 is all it'll do governed at 67ish, and it won't pull a hill worth crap. But it's more to do with the 9 speed trans rather than the engine. I have never driven a Cascadia, but this 680 has more room than I have stuff to store.

 

I used to drive a 13 cascadia dd15 with a 10 manny tranny geared for fuel economy goved at 65. 7.8 and up most of the time i liked it but any hill was an up hill battle. I currently drive a pac epa 13 w/ 13 speed and 3.36 rears. Mpg averages 7.5- 8s. Not goved but keeper around 65-68 when needed but rarely try to pass 65. She throws lights to keep you on your toes when heavy rain is a factor but wont throw a code. Just did the cam shaft recall i can tell the difference. Great pulling power. Overall i cant complain about either. Just thought i would chime in

 

Gearing is a huge consideration. Most of us need to really squeeze fuel, so once you get up above like 3.42's, your gonna struggle to squeeze that fuel. 3.55's and up, you can roll over a hill pretty well.

Depends on tranny too. I'm intrigued by the new generation Cascadia. That's supposed to really squeeze fuel.

But, if I can get on at LS, I'll just go back into The White Volvo Mafia.

Fuhget about it.