6.7 Cummins vs 6.6 Duramax

Cummins: Tougher than an old boot. Fewer parts. Mine has 410,000 miles and still going strong.
Duramax: Tough. More parts to wear. At one time, the connecting rods were lighter than those in a Cummins. I don't know if that is still true.
Of course, there are those who just can't stand to own an I-6 engine, they have to have a V-8. Many years ago, when I was a Ford aficionado, I felt the same way.
Years ago, I bought a '94 Dodge Ram 3500 CTD for heavy towing, and never looked back. For me, it is Cummins all the way.

I like them all so long as they smoke....

Without getting too much into the weeds, where this will soon go, there are some basic differences between the layouts. Both V8 and I6 have primary and secondary balance and make fine engines. A couple of the differences are:

Cummins - Inline six has 7 main bearings and long stroke crank. Better torque characteristics but slower spin up. Cast iron head and much work can be done while still in the truck. Heavy.

Duramax - V8 has 5 main bearings and a shorter stroke crank, quicker to spin. Aluminum heads and more difficult to work on due to V configuration.

Both are good formats, It's the bolt-on stuff that makes the difference in terms of reliability. If you are buying used, there were good and bad years with both.

Like a which truck is the best both are tops in that class. One isn't better than the other.
Drive them both and then you decide which one you like.
My self I prefer the white one in a crew cab 4wd.

In anything newer than about 2013/2014 its a chocolate vs vanilla argument. They're both great, but some like one better than another.

My Duramax is quicker off the line than my friends Cummins.

I have owned one or more iterations of every Dmax since 01. Bought them all new, and have been happy with them (never owned a 6.7). Like already mentioned the various years have their ups and downs but overall I think both the 6.6 and 6.7 are dependable and powerful. Resale is good to great depending on the model with both of them. The resale says a lot about the confidence the market has in them, even if you plan on keeping it forever, the fact that they have value even with high miles tells you about their perceived value. The decision likely will come down to the package as a whole. It is a good position to be in.

Since I'm not racing trucks I will stick with my Cummins diesel. There's lots of them rolling across the USA every day with over a million miles on the engine.

Our 2009 Duramax has been flawless. Number 8 glowplug is the only engine issue we've had. Had to replace upper and lower control arms, tie rods and shocks. 167000 miles and going strong, hopefully another 10 years with him.

SidecarFlip wrote:
I like them all so long as they smoke....

I'll drink to that! Roll coal brotha!