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'06 CLS500 '01 CLK320, '84 300D
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Discussion Starter · #1 ·
Since I am going to be doing all of this work this weekend I figure I would do an oil change too. Being that I am in cold weather, what do you guys suggest???

I have done some searching and Rotella T Synthetic 5w-40 seems to be popular, and inexpensive for synthetic. I am running conventional oil now but will switch to synthetic if it will provide a better experience.

Any thoughts???
 

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1991 300 SE
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18,534 Posts
In the cold synthetic may be the only way to go. I stay with 15w 40 Delo because it does not get cold here. Synthetic is good for cold weather starts.
 

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1982 240D M/T White
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196 Posts
I researched the available oils and went with Rotella Synthetic 5w30 when I bought "Otto".

I am trying for very long life and I like the reduced wear from synthetic. Rotella is NOT the best synthetic, but it is affordable (~$13/gallon at Walmart).

Also, Valvoline Synthetic Brake Fluid & Power Steering Fluid; Mobil 1 ATF for the manual transmission and 75w90 for the differential (with magnetic drain plugs).

Alan
 

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'82 W123 300D, '93 W124 300D, '01 W220 320 cdi
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130 Posts
Be careful with the mineral to synthetic upgrades especially if the car has high mileage. Synthetic oil has high detergent characteristics that might wash away the combustion ash that builds under the piston rings leading to loss of compression (fatal in diesel engines). The sludge washed away can also clog up lubrication channels and oil filter.
If a certain type of oil metes the long or extra long life service interval requirement, this does NOT mean that the engine does.
In other words- the MB w123 is not prepared for long service intervals.

RuffStuff
 

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'06 CLS500 '01 CLK320, '84 300D
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Discussion Starter · #5 ·
Well, my W123 only had 76K original miles. On top of that, it has pretty much sat for the last 4 years. Is making the switch to synthetic maybe not a good idea???
 

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1982 240D M/T White
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I forgot to mention that I changed my oil filter twice before the 3K oil change "just in case". At about 250 miles and again at 1,000. Almost certainly a waste of money.

I would suggest driving for one oil change on convential (collect all of the trash from sitting for 4 years), then change to Rotella with two extra oil filter changes.

Your compression is VERY unlikely to hinge upon a layer of ash on the rings. If that is all that is keeping it going, then you are not far from a new engine anyway.

Alan
 

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1991 300 SE
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In the past there were occurrences where existing minor leaks became major to the point of mandatory seal replacement. Miles and age can effect seals. I’ve read in other forums where newer synthetics have been reformulated to avoid the problem.

I believe these old diesels need frequent oil changes and what oil is used is less important. Any CH – 4 rated will keep the engine safe, if changed every 3000 miles. I would go so far as to say a good S rated oil would do no harm provided the oil is changed frequently. This in addition to possible worsening oil leaks and the added expense makes me comfortable with 15w 40 dino.

But in my climate I can afford to be flexible – a super slippery synthetic that flows quickly down to minus 50 F sounds attractive, especially with all the cold weather hard starting posts I’ve seen this winter (and last winter and the winter before that…)

My guess is with those low miles ring and valve train wear should not be an issue and dino oil would be a good and safe choice.
 
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