Does anyone have any proof a modern CJ4 or CK4 synthetic/blend 10w30 is inadequate for an older MB diesel like an OM617?

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'82 300CD
"Pearl", the very first turbo diesel 123 coupe
Totaled 11/23/18, rebuild in progress.
'85 300TD, "Artemis".
'78 300D euro, "Ol' Red", mostly retired.
'85 300D, "Gandalf".

Your owners manual

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Rindfleischetikettierungsüberwachungsaufgabenübertragungsgesetz

Introducing a thinner oil to an aging engine is a bit counter intuitive for wear and most inquiries into "30" weights seem to be strictly backed by the cost initiative alone. For how inexpensive (comparatively) it is to run a properly weighted oil, why even bother subjecting your engine to potential for failure? Just a thought.

For what it's worth, all of my diesels see synthetic oils: 15W-50 when doing long road trips through mountains, 5W-40 for regular use.
Do with that what you will.

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Allen Kroliczek
Oak Grove Autosport | Oak Grove Autosport
01 G500, 82 300TD, quite a few more.....

All the conjecture I can already find seems to be based, mostly, off of the old habit of overshooting viscosity so it doesn't get too thin when it "wears down" - aka, shears. Modern oils don't shear like older formulations did so the idea of starting with a 40 wt. so it doesn't get "too thin" isn't a thing anymore. If in decades past you were using a 40 wt. so it only thinned to a 20 or 30 wt. by the end of its usage, if a modern 30 wt. stays a 30 wt... why use a 40 wt.? Add to that better neutralization of contaminates, better thermal stability, etc...

If these engines lasted so unusually long when they were new, on the crappy, ancient oils of the 1980's, why is it so hard to believe a current oil in the upper end of the quality spectrum (name brand synthetics, for example) isn't total overkill and one step thinner oil is actually protecting way better than say, Castrol 20/50 did twenty years ago?

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'82 300CD
"Pearl", the very first turbo diesel 123 coupe
Totaled 11/23/18, rebuild in progress.
'85 300TD, "Artemis".
'78 300D euro, "Ol' Red", mostly retired.
'85 300D, "Gandalf".

I guess a better question to ask in this thread is: "Why are you afraid of using the weight oil your engine was designed for?"

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

10w-30 isn't a very temperature-stable oil when you compare the hi-lo numbers. Essentially behaving as a 10weight when cold (still fairly thick) and 30weight protection level at temp (not very viscous at 212*F). An oil with those two numbers further apart is going to cover a wider range of temperatures. A 5w-40 for example is still easier to flow at freezing temp (the 5 weight number) and still offers more protection/film strength at full temp (40 weight at 212*F). At any rate, heavier oil only has a few drawbacks besides the obvious pumping losses/fuel economy. You definitely don't want rev the engine high when cold on heavyweight as pressure will be skyhigh and I'm guessing oil flow will get bypassed instead of flowing to where it should go. Curious to know what the pressure cut-off is for the oil pumps on these older diesels.

My OM603 gets 15w-50, the 911 also gets 15w-50, and my Mazda which originally called for 5w-20 conventional gets a regular diet of the 0w-40 because 0w-40 is just a better 5w-30 in my eyes.

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{2010 Mazda 3 266,000mi} - daily since new, Airlift suspension + some chunky sway-bars: fastest pass 17.7@77MPH
{1987 300SDL 256,000mi} - stock turbo @ 22lbs straight piped + a whole bunch of pre-turbo water/meth injection, 722.3 with increased line pressure, special sauce, and shift kit: fastest pass 16.5@82
{1992 964 Carrera 4 Frankenstein ??,???mi} - 993 forward dated, Speedster conversion, GT45 + E85: fastest pass 12.5@113

Technically, it was "designed for" 30 weights under the right conditions, and it was also "designed for" Dexron II-D transmission fluid which happens to be hygroscopic. 40 years of technology advancement in lubricants might call for some reconsideration.

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'82 300CD
"Pearl", the very first turbo diesel 123 coupe
Totaled 11/23/18, rebuild in progress.
'85 300TD, "Artemis".
'78 300D euro, "Ol' Red", mostly retired.
'85 300D, "Gandalf".

No doubt 5w40 is a great grade and has a broad range of uses - that's what I've run in all but one of my diesels so far. But is a good quality 10/30 going to be truly inadequate, or even close, when it comes to film strength in the 617? It's clearly a very strong design and not terribly power dense compared to engines of the last ~20 years.

Just for fun I've been comparing the numbers on several of Schaeffer's products. Their CJ4 5w40 has a pour point of -41F while the two available CK4 10w30's have pour points of -43 and -49F. The 40 weight's viscosity at 40*C is 85-89 while the 30 weights are 77 and 82. So based on these numbers, the 10W's actually seem to have better cold stats than the 5W - or am I missing something?

Also, among the same oils the 30-weights viscosity are 11-12 at 100*C where the 5/40 is 13.5-15, but the 10/30's both have flash points above 460F while the 40 weight is 437F. Also the volatility test is a *hair* better in the 30 weights - 10% vs. 11. Based on these numbers it seems like the 10/30 is going to perform just as well when cold, and be thinner when hot but still withstand heat better.

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'82 300CD
"Pearl", the very first turbo diesel 123 coupe
Totaled 11/23/18, rebuild in progress.
'85 300TD, "Artemis".
'78 300D euro, "Ol' Red", mostly retired.
'85 300D, "Gandalf".

my gas ,and diesels get the same 5w40 winter 15w40 summer. Older oils have anti wear chemicals,I buy only gallons,as five quarts hard to handle. CDI's are eating timing chains with thin dealer oils.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

You're going to do whatever you're going to do to your engine. Nobody's going to stop you doing it. If you want to run 10W-30, go ahead and do it, nobody's holding a gun to your head to use 15W-40 dino oil.

No. It was designed for 40 weight oil and designed to operate satisfactorily when the oil diluted and "sheared" down to 30 weight. The design of the engine has tolerances and oiling considerations expecting the characteristics of 40 weight oil. 30 weight oil should work if you keep it changed frequently. This is an IDI engine, expect fuel dilution and expect thermal and viscosity breakdown from the turbocharger and piston oiling jets. I don't care how well maintained your car is or how good your oil is, it WILL thin as it ages. If you're fine with running 20 weight oil after dilution and breakdown in your diesel, get after it. Nobody's stopping you.

You're now comparing apples and oranges. Dex II is obsolete and replaced by Dex III and Dex/Merc blends. They're more or less direct replacements for Dex II.

10W30 is NOT a direct replacement for 15W40. If it was, it would have the same viscosity rating. Flash points, pour points, and film strength are great, but the viscosity plays into an overall role in the oiling of the engine as well. If all oils performed equally well, there would be no viscosity rating, but they don't and so there is.

Unless you live in Siberia or Saskatoon, there's no point running thin oil. Any modern 5W-40 or 15W-40 oil is going to be adequate in just about any climate. If you're a responsible vehicle owner, you're going to be changing your oil on a routine cycle anyway, so why does it really matter?

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

I have run 10w-30 Rotella T4 in my MB240D when the temps get below 70's, as per the owners manual. Was the motor originally speced for synthetics? I don't remember that in my owners manual.

Does this oil meet the specifications for a mb diesel?

CJ4 or CK4 synthetic/blend 10w30

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Actually there is evidence that increasing viscosity over 100K miles is not a bad thing. Some years back after my brother in law used some Walmart oil in his diesel. The engine made new noises so he changed it.

It could have been a mislabeled batch. Chrysler advocated a 10-30 oil in there new smaller truck diesel with bad results.

The side thrust loadings on the pistons are higher on a diesel. You want the oil cushioning effect.

We live in the Canadian Maritimes where really hot temperatures are not that common. All the old guys like myself believe nothing less than 15- 40 weight oil in old diesels.

Manufactures today want the lowest viscosity they think they can get away with. To enhance fuel millage.

I have 5w40 semi synthetic in mine. Runs good.I won't use thinner than this if the engine has over 60000miles. Due tolerance differences in the main bearings.

Thanx for all the thoughts gentlemen .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better