I'm a very hard-headed type. I inquired about synthetics, read all the posts and asked my mechanic.

He warned me that he had tried synthetic twice on older SD's and both started using oil. They resolved this pesky habit when he switched back to regular oil.

Undaunted by professional advice, I bought the 5W40 Wal Mart Rotella and gave her a shot. Seemed quieter on start up, even though I'm in Florida, I liked the idea. My 83 300SD with 160K seemed to run about the same and maybe leaked a tiny bit more.

After a few trips, I thought the old girl was smoking a bit more at night under acceleration. I noticed a puff of smoke on early morning start up's. Sure enough, the oil level dropped a little, and I noticed oil residue from the oil fill cap very slightly and blow by on the vent to the air cleaner.

I switched back to Delo 15W40 and after a 100 mile trip today where I pushed 80 mph on cruise most of the way...no oil from the oil cap or any evidence of blow by.

I learn the hard way, but don't forget these lessons.

Just thought I'd share my experience with any of you who might be thinking along the lines I did.

It is always a risk on older engines that the synthetic will leak more than dino, since it tends to lower viscosity cold.

What that really says to me is that you need new valve guide seals! Minimal oil usage with dino oil, but more with the thinner synthetic.

If you decide to try again, use 15W-50 rather than 5W-40 -- 5W oil is too thin for an old MB diesel except where it is VERY cold.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Depends on the vehicle. Dino to synthetic in the Jetta and the 300D, no issues. RT

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When all else fails, vote from the rooftops!
84' Mercedes Benz 300D Anthracite/black, 171K
03' Volkswagen Jetta TDI blue/black, 93K
93' Chevrolet C2500HD ExCab 6.5TD, Two-tone blue, 252K

MB recommends Mobil 1 0-40w as the synthetic oil to be used in all MB motors. You will burn oil, about one quart 800-1000 miles, for about the first 5,000 miles or so. Then you should see less and less oil consumption. Oil change is about every 20,000 to 25,000 miles, instead of 3,000 miles.
Your best interest is to switch to Mobil 1 and save money, as the dealer or garage will lose money. The mechanic best interest is to change the oil, the old way, every 3,000 miles and take your money with a smile. Go back to Mobil 1. Synthetic are the future and there are plenty of people who rather you stay with dino oil.

Bill

Shark,

I don't think you gave the Synthetic a fair chance. You have to use it for 10, 20, 30 thousand miles to see the results.

I use Castrol Syntec in a '79 300SD and it decreased the oil consumption by a factor of 3 I.E. from 3 quarts to 1 quart in 10,000 miles but it took 30,000 miles to do it. It also stopped a few oil leaks the engine had. I change the oil every 10,000 miles.

P E H

We are talking about a old DIESEL engines here...and they seem to enjoy a good grade of Dino oil 15W- 40. I ran heavy equipment throttle wide open... 10 hours a day... 6 days a week for over 20 years with NO oil problems. I changed the oil/filter often and knew of no one that had problems...these are older CAT engines with no direct injection... just like the 617 engines. I like synthetic oil in gas engines and when it is very cold...but DIESEL oil is made to deal with the soot in the oil. Newer cleaner burning engines and synthetic oil are the future...I agree....but we are dealing with 15 to 30 year old engines. " if it ain't broke ...don't fix it"

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1983 300SD 343K everyday car
1983 300SD 285K from junk yard-tooks parts from deer car- runs great. Brothers car.
1984 300SD parts car-Hit deer
1979 300D 175K non-turbo "Doctor"
1979 300d parts car

My 81 300 TD is a old Mercedes design. This design can allow the new synthetic oils but within a narrow band width. Other types of synthetic will not work. You must know which syn oil is good for your designed diesel. Diesel design varies from manfacture to manfactures and so will the type of oil recommended.
The soot level in a MB diesel should not be more than 3 percent. If it is, change the oil. There are plenty of companies which analyze the oil and state the soot along with many other things. A good tool.
The idea of " if it ain't broke ...don't fix it" is a old idea. You must find yourself broken down on the road many a time. Parts are designed with a useful life in mind, change it before it reaches the end of it's design life. It's called preventive maintaience ( spelling) or time changes on aircraft. Ever think about waiting for a airplane engine to break in flight- you can but not me.....

Bill

Those of you who have switched to synthetic, did you all go with Mobil 1? Also, how did you go about it? Did you just do an oil change and put synthetic instead of dino oil in, or did you do some form of a gradual process, or what?

I've already done the differential with Royal Purple synthetic; I'd like to do the tranny (that's another thread), but have always gone with dino oil for every engine I've had, due to the old fear of creating oil leaks that I didn't have before...

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2001 VW Jetta TDI, 5 speed, daily driver
1991 Ford F-350, work in progress
1984 Ford F-250 4x4, 6.9l turbo diesel, 5 speed manual
Previous oilburners: 1980 IH Scout, 1984 E-350, 1985 M-B 300D, 1979 M-B 300SD, 1983 M-B 300D
Spark-free since 1999

Warden,

I just did an oil change and filter change as soon as I got the cars, both 3000SDs. I used Mobil 1 15W50 in the car I use in the summer and Castrol Syntec 5W50 in the car I use in the winter because of the wider viscosity range.

P E H

With both cars as soon as I got them home they were changed to Delvac1. Within a week I'd change the tran's to Mobil1 ATF, Mobil1 ATF in the PS steering pump and Mobil1 Gear Lube in the differential. Because I've never driven my cars with dino oil I've never noticed any increased leaking. The SD is oil tight. The 240D use to use a quart every 1k mi., this is now down to 1qt every 2k mi.

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Fred Johnson
1977 240D
1983 300SD

I have changed over to Amsoil 15/50 in all my MBs and am very happy, no increase in oil consumption. In fact it seems that its gone down. I ran tugs for years and Delo 400 was the oil of choice but that does not mean that there is not something better out there now. BTW I use synthetic ATF in gear boxs and power stearing.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Chapp,

What type of injection did the CAT engines have? Did they have precombustion chambers like MB?

I know the older engines, with pony engines to start them, were very hard to start when cold, which would suggest precombustion chambers as they are harder to start when cold than direct injection engines.

P E H

When the weather turned REAL cold here, I stopped the Chevron Delo 400 and put in Rotella SB 10W40 synthetic blend. At 8 degrees fahrenheit the oil pressure gauge was staying pegged 30 seconds after I stopped cranking and it was cranking pretty slowly too. Unfortunately, the small oil leak I had has gotten bigger. Not enough to tear down and replace the rear main seal, but annoying. When the weather gets warmer I will change back to 15W40 and hope the leak goes away.

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83 M-B 300D- daily driver
83 240D gray market
2002 VW Jetta TDI- beater

I have been running 5W40 Rotella Synthetic for about 1000 miles now, and I have found that I am using less oil than with 15W40 Delo 400. Before I was using about 1 quart for every 900 miles, and now with the 5W40 it's up to 1 quart for every 1000 miles. In the summer my oil consumption is alot less.

Interesting...I work (at the moment; looking for another job) for a tug/launch company, and they're using different stuff in different engines; divided pretty evenly between Delo, Royal Purple, and Mobil 1 synthetic...ironically, all the 12V-71's use Royal Purple straight 40 weight...and use quite a bit of it I think the last boat I worked on was taking a gallon and a half per day per engine...