I've been using Castrol 20w-50 in my 1980 240D manual with 273,000 miles for about 10 years. It was previously running on the same weight but Valvoline 15 years ago when my father passed. It has always been a warm weather Southern California car but I have no clue what weight he was using. No leaks and the engines clean but my question is should I switch to a synthetic since it's getting older? Or don't fix what is not broke....

1980 Mercedes 240D manual 273,000
2015 Ram 1500 EcoDiesel Turbo 30,000
2015 Jeep Cherokee EcoDiesel Turbo 20,000

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Well, how often do you change it?

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'82 300D (project)
'46 Willys (project)
"Nothing seems to be the way it should in this garage." -jt20
"Smarter than an engine, dumber than a hoodlatch..." -jt20
"Start jumping up and down to smoosh down those engine mounts" -DeliveryValve
"no" -kerry
"At this rate, you may have it done by winter" -layback40

Every 5-6 months since I only put 3,000 miles on it a year.

Is that a diesel blended oil? C-J or better?

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

There is no right answer in an oil thread.
Change to syn if you wish, I've switched more engines to synthetic in the last 40 years than I can count. Completely your choice.

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Gone to the dark side

- Jeff

You should be running a diesel rated oil.It has things to hold and coat the carbon so it won't wear out parts.You can go 5000 miles before changing it. If you want the protection of syntheic 1 part to 3 parts dino will give same protection as full syntheic fill.Unless its winter in high northern states i see no need for syntheic diesel oil. I run 15w40 all year in my 617.I even use it in all my gas engines.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

Many different opinions follow oil threads...so here is mine. Stay with Dino and get a C rated oil not an S rated. As for weight a 15W-40, as for brand, I like Delo and Rotella.

Use high quality filters and change it when the oil is hot.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

I agree w/ post #6 that a high detergent "diesel" oil (CJ rating) is most important to suspend the black carbon. You can get it in synthetic, but since it gets black fast it seems better to change it often, say 3000-5000 miles, so synthetic seems a waste. I will add that changing oil every 1500 mi is expensive, wasteful, and bad for our earth.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

My 84 and 85SD both start much easier in the winter on synthetic. I sent an oil
sample from my Cummins to Blackstone and was told that the oil was still in good shape and that the change interval on that engine could be extended to 15,000 mi.

Granted, a 24V Cummins is not a 617 and perhaps will send a sample from the Mercedes just for information purposes. The Cummins takes 3 gallons and the 617 ~2 gallons so the economics of paying for oil samples is different.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

In your climate. The 20-50 normal oil as long as it is diesel rated. I personally would stay with that.

It is probably about as close in reality to the original straight 40 weight as is practical today.

"Or don't fix what is not broke...."

That says it ALL!!!!!!

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96 E300d

When we got our 80 240D from the original owner, it was at 305,940K. That was almost 6yrs ago.
We are now up to 388,798. Used 15w 40 diesel rated oil.

At 322K I switched to a full synthetic 15w 40.
Oil use age did not change or did it cause any additional leaks. She uses a qt around 1200 - 1400 miles.

Actually Iam surprised at how dry this engine stays. I do get a drip on the floor now and then.
This engine has not been rebuilt, all original.

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

On these old soot collectors the frequency of change is perhaps as important as the oil used. A periodic highway run is needed to get rid of any accumulated condensation in the oil. Prevents sludge formation as well.

You have to get the oil to 212 degrees to boil it off is why. The pertroleum oil does not boil itself till 400 degrees or so I believe.

If you are only doing about three thousand miles a year and changing the oil twice. I would only change the oil filter every second time.

You are probably too young to remember. That one time every thousand miles was the recommended oil change interval on many cars.

At a burn rate of about 1200 to 1400 miles per quart that engine should have a lot of life left. That's if the fuel pressure in the base of the injection pump is still decent. It should be checked at that milage and corrected if needed if it never has been.

I'd like a look at those results.

I'm curious- what, and/or where is your source of information on this? I'm not intending to be critical at all.

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Marshall Welch
Seattle, WA
1982 300D-T