I had a friend who worked for the railroad and he told me the story of the extensive testing on diesel engines the railroad has engaged in for years. He always said they eventually always came to one conclusion:

You could have as many cylinders as you wanted, the only catch (for longevity's sake) was that they all had to be in a row.

And that's the primary reason for the longevity of these Cummins diesels.
Mine? A mere virgin 1993 vintage 2wd I bought new presently with 243,000 & with the original clutch....still.
While the Duramax's and the Powerstroke's maybe "powerful" their 8 cylinder V-8 configuration dooms them to likewise longevity as our Cummins powered trucks. Fail to take care of them and they'll go away even faster..... Chuck

 

Why though?

 

Main one is more bearing surface area. It displaces the load over more area = less stress on components. There are a few valve/pushrod/cam reasons too. The cummins has 7 huge bearings for the crankshaft. Powerstoke and the Duramax have 5. Pistons to bearing ratio cummins 6-7 all v8's 8-5. The advantage wont be noticed untill higher mileage. Your cummins will be running like new at 250000 and theres will be more worn out. There are a lot of reasons. More than I can even begin to explain I hope some others will post.

 

Wow! That's almost hard to believe! Are you sure you didn't rebuild the engine inbetween? Joke.. This just comes to show that cold starts really do have the hardest hit in the life of an engine. I'm sure your truck has been running for most of it's life. No way can you have that many miles in only 7 years if you turned it off frequently..

I've got 280k on my truck and it's running like a champ. Just changed the clutch. Oil is still clean and it doesn't use it or leak it either. Knock on wood...

As far as engines, I'm not too familiar with the internal dynamics of an engine but just take a look around. Inline engines tend to outperform V engines. I think the only reason they designed a V engine was due to limited space in the engine compartment. This way they could fit larger displacement engine in a smaller area. Could gravity play a role in the longevity of an inline engine as well? If you think about it, since the pistons in a V engine are slanted, there is always a little more weight on one side of the cylinder.

 

This is a theory that's been around since the Ford flathead V8, but it doesn't work that way. Compared to the side loads from rotating the crank, gravity is nothing. Wear on the thrust side is always more than on the compression side. Trying to compensate for this is one reason why pistons have a front and a back - the pin is offset.

Not many V-8 diesels make it to 500k, but wearing out the bottom of the cylinder bores is not one of the reasons for that. I think the "fewer main bearings per cylinder" theory has a lot to do with it, as well as the typically smaller rod length/stroke ratio (faster piston speed).

 

Even gassers that are inline last longer....look at the Ford 300s, I know of 2 that went in excess of 400k without a rebuild...inlines are just better.

 

I have to agree, no matter who builds it the inlines can get it done.

Chevy 250's,292's Fords 270's,300's and Mopar right down to the 4.0l that many Jeeps have going higher miles.

 

at my grandpas john deere dealership he claims a 91 has over a mill and 2 are reaching it

 

I've always heard that it is because the inlines are balanced better...but what do I know

 

The only problem with your quote of you friend is almost all locomotive engines are v-16 to v-20. Not that I dissagree, I do think inline is the way to go but a locomotive engine would have to be a lot longer to get 16-20 in a row.

 

My 90 Dodge 245000 Wifes 91 145000 81 Volkswagon diesel 531000 82 Volks 1114000