I didn't mean any disrespect honestly, I apologize if it came across that way.

I'm also well aware the 603 heads are prone to cracking and this is not related to oil changes. I just find it surprising that someone drives around with a blown head and does 10k+ mile oil changes. The factory manual/book no longer applies to these vehicles at their current age and mileage.

Change the oil often, around 3k miles, use quality filters and oil and you'll be safe. Yes, this is my opinion, along with Kent (someone who has taken 100's of these engines apart).

Watch the video - https://www.youtube.com/watch?v=y4VqcghARzg

The factory maintenance manual absolutely still applies to these vehicles. If it was good enough to keep them going when new in the 80s with inferior lubricants, coolants, detergents, and protectants, then the schedule that DB recommended then is MORE than adequate now.

I subscribe to Kent's channel and I've bought some of his products. He definitely knows what he's doing and I respect his opinion most of the time. However, he's also preying on people like you making you think that OM617 is made of glass and if you so much as look at it sideways it'll break and you'll be a saaaaaaaaaaad panda. That just isn't true, it's mostly marketing to bolster sales of his products. He isn't wrong, he isn't even being dishonest, he's just promoting caution to people who don't know otherwise.

Sorry I disagree. I just talked to two Mercedes Benz mechanics that also disagree with all of these details. I'm trying to get them to sign up for the forum to join this discussion, because it's a good discussion. These were old school mechanics that worked at the dealer in the 90's.

If we both drove two OM617's/616 or 603's over 30+ years, the exact same way and I changed my oil every 3000miles and you 7500miles using the same OEM oil, filter, I would have significantly less ring and overall engine wear then you.

I'm talking about compression, actual ring play/wear, timing chain stretch (using a dial gauge), and just overall cleanliness of the engine along with oil analysis results.

I have friends who have run oil analysis on their oil at 10-12k intervals using M1 on 250-300K mile 60x engines that came back and still fine, probably could have gone 15k without a problem.

This thread made me laugh. Thanks!

I use 5w40 synthetic every 10k miles. I've done it for the last 80k miles when I got the car. Now has 230k total. Just before pulling the cracked #14 head I did a compression test. All 6 cyls were above 400psi. It doesn't get any better than that. As for "overall cleanliness, here's what 10k mile oil changes look like.
https://i.imgur.com/NmlHjbr.jpg?1

https://i.imgur.com/z4bGhlx.jpg?1

https://i.imgur.com/7BLddM6.jpg?1

https://i.imgur.com/eJ34Ayu.jpg?1

https://i.imgur.com/uaGgccT.jpg?1

https://i.imgur.com/fuLhZ0i.jpg?1

I think the issue with diesels is much more carbon buildup in the oil. The main difference in diesel oils is more detergents to suspend the carbon. Thus, the main reason for regular oil changes is not that the oil has chemically broken down, but rather the carbon load is too high. If true, I would think regular oil changes of mineral oil at 4000 miles is better than running synthetic oil for 7500 miles. Most gas engines now have optical sensors which measure how dark the oil has become to flag a change. Probably wouldn't work on a diesel because even after the first day of driving my new oil looks blacker than in the least-maintained gas engine.

I'd be comfortable with 5K changes on a quality synthetic oil. In Cmac's case I'd not worry too much about running an extra 400 highway miles.

Tittsi's pictures are pretty convincing.

What I feel about oil changes. Is just get it changed at whatever a reasonable interval to you is. Try to make it as easy on yourself as well. I recommend no oil type to others.

Other than staying away from oils like walmart sells under their own in house label in five gallon plastic buckets. Their gallon jugs and quarts may be no better. They are a high margin company and consideration for the customer is not their operational mandate. Whoever supplies that oil does it for a sub standard industry price. To do so indicates it is not even of average quality.

People may be a little too rigid. If a car of ours is used only locally 90 percent of the time on short trips. Say of five miles or less one way.I Get that oil changed more often. If another car as is in our case sees four to six hundred miles a week highway service primarily. It can go a little longer than average. Then there is the claimed six month rule as a guide to changing.

I have never thought about that much or looked for a description of why. At the same time sulpheric acids and perhaps others do accumulate in the base oil of gas engines. Possibly not burning off. Other than it is totally not milage related.

Base oil is far cruder than diesel fuel that does not seem to oxidise in my experience usually. Base oil is also contained in a semi sealed situation. This applies to normal petroleum based dino oil. Synthetics on the other hand seem to use many variations of their base component.

In my case after all these years. I am switching over to vacuum extraction. Making it easier in many cases will just get it attended to quicker usually as well.

I find scrounging what is needed to make a vacuum setup. Or many other things is almost becoming a lost art. Most like myself do it perhaps because when we were very young there was no other reasonable option at the time. In addition I like building things. So it became a developed skill set. Too much general affluence has resulted in this not being as common today as it once was. I really believe all our four children very seldom engage this approach. Or ever really learnt how to go about buying things.

It is strange what time works out like. For some available time presents no issue. In my case as perhaps in many others. If I can do it faster and easier it does not tend to get deffered to when I have more time as often.

I probably would be far less diligent with an obviously already tired engine. I also would use a higher viscosity oil as well to reduce the oil burning in them. Plus hopefully add some additional protection from worn parts coming into physical contact by doing so. People forget that the more wear present the quickening rate of even more occurs.. At this time fortunately I do not own any fairly worn engines.

Do not buy high engine milage oil unless you have leaking seals. Still tight seals do not need it. Technically it could even cause them to leak in some cases.

Use only German labeled brand oil filters for german cars. Simply because they have substantially more filtering medium internally usually. On Japanese cars try to use oem filters.

Companies like Toyota do not have specific demands on using their oil. They do have demands on using their oil filters though. Especially during the warranty period. Aftermarket filters are known to come apart and destroy their engines.

They are cartridge insert types and possibly break up and block the output port of the filter housing. Or more likely engine oil passages. Under warranty if they open the filter cartridge holder up..Finding the aftermarket filter cartridge has probably done this. No replacement engine will be supplied.

After warranty the engine lost can and will be on you. You can usually source good oem oil filters in small bulk orders just as cheap as some of the aftermarket ones. Sometimes even cheaper. There also has been a shift in aftermarket item pricing. Many times today you can get the part from dealers cheaper. For example I think our Toyota oil filters are about 4.00 dealer sourced up here in Canada. Probably 5-7 dollars at the auto part chain places for an aftermarket one.

I left this post and checked. At the largest auto parts chain operation in Canada. The oil filters start at 6.95. Go all the way up to an insane 18.00 for the gold plated version for the same car. Obviously servicing the people who think they are somehow getting more because It costs more.

Marketing hype still works in general I suppose. Many things contribute to keeping the economy afloat.

Trying to find examples of these older cars in better condition overall. Even if a little more costly initially. To me common sense indicates. Their base engine oils just may have been changed more frequently. I really dislike the expression of win win. At the same time this could easily apply to them.

Nope. My 99 E300 with half a million miles on it has seen oil changes every 7500 miles with Mobil 1 0w40 since it was new and only had a top end rebuild at 412k and a timing chain and guides at the mid 300s. I also had an e300 with 410k on it and had only a timing chain and guides done to it as well. That car followed 10k oil change intervals out of the manual with synthetic as well. ;)

None of my 606s have any compression issues on the bottom end and don't burn any oil.

There's also a 500E (gasser) with an original motor at like 450k following 7500 mile oil changes of synthetic on an original engine. It's on the 500E board somewhere.

The best way to answer your question is to send an oil sample into Blackstone Labs. In the comments section ask them what you could extend your service interval to. I use a synthetic on all the vehicles the recommendations vary.

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I get infuriated when I see people write posts like, "change the oil every 3k miles".

Get a dang oil test done for $25 and find out exactly what your oil looks like. They told me I could go to 7k miles on my 300D.

3000 mile OCI seems a bit low, I could see that being a good number back in the day with older oil technology but the stuff we have now is alot better.. 5k is completely safe. Like said earlier the golden standard is to get a oil analysis and see for yourself, that's what semi truck drivers do. They also run alot more than 5k, lol

This was a thought I kept coming back to. I went from '02 to '16 using mainly BMW E30 325i (s plural, not sport) as daily drivers. Going 7k on synthetic makes more sense with those than with a diesel.

I found some Rotella T5 15w/40 at a WalMart for $18 a gallon, I can get a WIX filter at O'Reilly's (I have a Mann at home, I'm still 750 miles away, can't get a Mann off the shelf here). My impression is that WIX are generally good filters, I'm going to try to change it at my nephew's house today. I'm at 5036 since the last change.

I appreciate the feedback, I get that this topic is often an area of some dispute and controversy.

That's a good vid, his point is well taken. Rings. Rings. And cylinder walls. He's got me thinking on the business of going with the T5 part synthetic. I had read once before that synthetics make more sense with new engines. Switching when old not necessarily any better.