5 cyl vs. 6 cyl diesel
 

I'm not new to diesels, but I am new to Mercedes diesels. I had a VW diesel for years but I'm moving up to the major leagues. I'm trying to determine whether I want to go with an '81-'85 5 cyl 300 or a post '85 6 cyl 300 model. Both seem to show significant longevity, and it may be very subjective but which is better? What is a reasonble expectation of mileage for the 5 cylinder vs. 6 cylinder? How much does the turbo add mileage wise. These are very basic questions for such a learned group, but I can't think of a better group to ask. Thanks for everyone's help. I live in Virginia and I am currently looking. Actually I am currently waiting for the current tornado warning to pass thanks to the remnants of Tropical Storm Cindy. Need to sign off before I get the inevitable call to go to work.

the five
 

is generaly agreed to be about bullletproof as an engine.

the sixes from 86 to mid ninties or so have some issues that can be pretty bad, but when running good are really nice driving cars. also the older cars ac is marginal. otherwise the cars are very similar if you are looking at s classes. they all are 126 bodies. in 86 or so the e class came out. the e class motors are five cylinders or sixes. the fives are pretty bulletproof here too. the e classes are generally not as mechanic friendly as the 123 bodies and 126 bodies.

The OM601 (4cyl), OM602 (5cyl) and OM603 (6cyl) engines will be the most familiar to you if you're used to VW diesels (cast iron block/aluminum head w/lifter buckets). IMHO, the OM602 as found in the '87 190D 2.5turbo (very rare) and '90-'93 300D 2.5 will return the highest level of fuel economy, performance and reliability of any diesel engine North American MB offered to date. In addition, the chassis these engines are found in are far superior to the older model Benzes. For example, I own an older W123 chassis w/OM617 (cast iron block/head) that I rely upon for running errands, must-make-it-there trips, and backup, but my true love and object of my affection is a S124 chassis w/OM603 (6 cyl) for it's heavenly ride, handling, comfort, performance and fuel economy--there really is no direct comparison.

The 5 cylinder (617) is louder, durable, and seems like something of a throw back. It's hard to hurt unless something silly happens to it. Just a very solid motor... simple to work on. The 6 cylinder (603) is a bit more complex but not much, no need to be scared.



The 6 seems more refined, I supposed due to the firing order. It's much quieter and idles differently. I haven't had a chance to really drive mine much as I've owned it a week and have been out gathering parts in my off time. My tie rods are bent so it only goes about 30mph lol

603 motor does crack heads if over heated, it happens but you just have to keep the eye on the vital signs. Something you should do anyway. I'm very pleased with this vehicle so far, seems like it will be load of fun.



The 603 is what 143hp vs 120hp and I believe torque went up from 170tq to 195tq also, so it should run a bit better too.

It is easily summarized. The later six is indeed more refined and is superior WHEN EVERYTHING IS RIGHT WITH IT. Given the iron head of the earlier four or five cylinder, it is more trouble free.

Good luck,

How about coming at it from another angle? Decide whether you want a W123, W126 or W124 then learn to live with the engine that comes with it.

Sixto
95 S420
87 300SDL

Depending on the year and model

W126
5-cylinder OM617 300SD
6-cylinder OM603 300SDL

W124
5-cylinder OM602, E300D 2.5L
6-cylinder OM603, E300D, 1987 only
6-cylinder OM606, E300D.

W210
6-cylinder OM606...

Isn't this fun? ;)

Wait, it even gets better.......the 1987 300D, is the fastest of the whole lot. Imported by MB only one year to the US, the 87 [U]was the fastest production diesel automobile in the world...WOW.....and still get 30 mpg.

Todays MB diesels are even faster, but $$,$$$ :eek:

Thanks for everyone's help, I've got something to work with. Now comes the waiting game to find a good one.

What body was the 1987 300D?

My answer is that the 606 is the sweetist diesel MB has brought to this country. 4 valves per cylinder with double overhead cams, it will rev sky high and pull like crazy in turbo form. They are also extremly durable and seem to return extremly good mileage. I think as the years roll on 606's will prove to be very very long lived. I have seen some nice tight examples with 300k+ on them.

The 603 comes in a close second for me. They are extremly durable and are fun to drive as well. The 603 has a very nice sound at full throttle and returns good mpgs.

Both of the above engines have no problem in the winter.

Now the older 617 is a good engine, but it is not as powerful or returns as good mpg's as the newer motors. Also dare I say this they don't seem to last as long and hold up as well.

W124 just like the ubiquitous 300E.

Sixto
95 S420
87 300SDL

Bite your tongue, HG, eBay is full of 617s with 500K - million mile potential :)

Sixto
95 S420
87 300SDL

What about the 602 compared to the 603 or 606?

I have never driven or worked on a 602, but they seem to be good engines. I almost bought a 1992 300D when I was hunting for a MB. It had 290k on it and was in very, very good shape. If the guy wasn't asking to much money for it I would have bought it.