Which is a better engine: 12-v Cummins 5.9 or Merz 300 turbo?
 

Hi guys, my stepdad and I got into a little debate over this last weekend. FWIW, I was arguing for the Cummins -- my position was that it's twice as big yet gets almost the same fuel economy lugging a three-quarter-ton pickup around as the Merc gets pulling a sedan body, and never wears out. He shot back that it's just because the Merc body is built to the same standards as the engine, that it still looks good at half a million miles but a Dodge pickup is falling apart around the engine by that point, which makes the engine look more heroic in comparison. He then goes on to tell me there are 617 engines with a million miles on them and he doesn't know of any 5.9 Cummins that's made it that far without a rebuild.

Hey, he might be right. Whadda you guys think?

Considering vehicle designs, Mercedes wins.
Considering engines, I'd take a Cummins over a Benz, but it'd be close.

I'm wondering what you consider "almost the same" as the 26 mpg I get in my euro.

My only complaint with the newer diesels is they all now have electronics controlling them. The old MB's don't have the electronics to mess with and to me that makes it a lot easier to work on. Once they add all the electronics it might as well be as gasser.

The Cummins might be interesting, but it's surrounded by a truck.

I've driven both and I would call it six of one and a half dozen of the other.

Don't say that there have not been 5.9 Cummins go a million miles until you have some firm data to back that up. I've never done any research on it, but I would be SHOCKED if there aren't a number of them that have made a million miles. I sure shudder to think about how bad the cab rattled at that point though. The worst part about driving a Dodge pick up is that every time you slam the door, your first inclination is to roll down the window and look out to see what fell off.

http://forums.motortrend.com/70/88046/the-general-forum/check-this-out-million-mile-dodge-3500/index.html

http://answers.yahoo.com/question/index?qid=20070724124252AADxNJ3

I just googled "Dodge Cummins Million Miles" and this is a couple of what I got.

I know the Mercedes engine has replaceable cylinder liners. If you really want to, you can restore the engine to something resembling a "no-wear" condition.

Does the Cummins 5.9 have replaceable cylinder liners?

Ken300D

Assuming that it wasn't the whole door that fell off... :D

I love my 92 Dodge/Cummins truck, but it's more about the drivetrain than the truck itself. It's got almost 270K on it and the engine runs like it's new, but the body is fast disintegrating. Awful early 90s paint job peeling and flaking away everywhere, cowl cracks that leak water into the cab whenever it rains (there actually used to be a cowl patch kit available from the dealer because this was such a common problem, even on low mileage trucks!), doors that are literally about to fall off their hinges, seat beaten down into nothing, window tracks that are repeatedly falling off the windows, and all kinds of little fleeting electrical glitches that are nearly impossible to track down.

The only thing that has ever gone wrong with my engine in the nearly 100k that I've owned it is that the in-block oil cooler spring a leak. It was a nasty, awful mess to clean up, but the part was not that expensive, and the repair was easy. While I had it apart, I pulled the oil pump and measured it for wear and it measured as having literally no wear at all, at over 250k miles. I've seen pictures of the cylinders of an early 12 valve engine at 350k that you could still see the cross hatch pattern in. I've got no doubt that one of these engines, properly cared for, could last a million miles.

That being said, I'm pretty excited to finally have a good Mercedes diesel, too. I used to have VW diesels, but the last one I had dropped a valve only 2000 miles after putting on a "new" head (I suspect cheap, non-VW valves were used), and I decided I wanted an all cast iron engine instead.

The Dodge Cummings is a great engine in a crappy truck. I know from experience that the engine is good for 750,000 miles plus with just normal maintainence - oil, filters etc.

The Dodge undercarrage & drive train give a lot of trouble long before they should.

Mercedes 617 is a good engine but most don't make it over 400,000 miles without a rebuild. The Mercedes body is very well made but the undercarrage and drive train require considerable rebuilding to make the 400,000 mile mark.

Just my opinion,
Joseph

I did have to replace the Getrag 5 speed in my truck at just over 200k miles. At that time, parts were expensive for that tranny, and no one wanted to rebuild it, so I upgraded it to a New Venture instead, and have been really happy with that choice. I have had some minor front end issues, and I'm due for kingpins now, too, but nothing major. All the truly worn out stuff is in the body department.

You'd be hard pressed to find an OM617 that reached a million miles. Likewise you'd also be hard pressed to find a cummins diesel truck that legitimately gets over 30mpg (driving my SD on the highway yielded over 30 regularly). There are a lot of myths out there...call Jamie and Adam!

I call bull. You don't get the same mileage out of the Cummins as the 617. Besides, they are for different applications. Dodge put a 50,000 mi truck around a 500,000 mi engine. For proof, look at all of the cracked dash, steering, suspension, KDP & transmission threads on the Cummins forums. It takes $2000 in aftermarket parts to make the truck NEARLY what it should have been from the factory. Switch to the 24V Cummins & add $1,000 VP failures with requisite tow bills to the list. Anytime I think there is a problem with the Dodge, there is a problem & I get out the checkbook.

SD problems have been limited to climate control & filters. SD has 240,000 mi, Ram has 150,000. Absolutely no way that the Dodge is as reliable. On the other hand, SD won't tow the boat. It is getting hard to find a 12V in decent shape & only the 98s had back doors.

Of course you don't. That's why the word "almost" is in there, to account for the difference between my old 23-mpg Dodge truck and my stepdad's 25-mpg 300SD.

Okay Guys! Let's stop comparing oranges to apples here!

The Cummins under discussion is in a truck that weighs more than half again as much as a 123 MB. This truck also has probably AT LEAST half again as much frontal area with a MUCH worse aerodynamic coefficient.

Fuel mileage is determined MUCH more by weight and aerodynamics than it is by engine size.

When I bought my '91 one ton, flat bed dually, 5 speed Dodge Cummins, I came out of a one ton dually, flatbed Ford 460 Four Speed. Pulling 15,000 pounds with the Ford I got LESS THAN 5MPG. Pulling the SAME 15,000 pounds with the Dodge took me to 14MPG. I thought my first fuel bill was a mistake.

Now, go figure ton/miles per gallon of a 3,500 pound 123 at say 30MPG and then go figure ton/miles per gallon of a 20,000 pound gross weight Dodge and gooseneck trailer at 14MPG and see which one is more impressive.

It is interesting to discuss the venerable Cummins and the venerable MB 616/617 in the same thread, but DON'T get carried away with the comparison of oranges and apples.