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oil question

Started by rumb, 11 September 2018, 05:53 PM

rumb

Ive used Rotella in all my older cars for years.  I also know that oil technology has changed greatly in the last 50 years. I am currently rebuilding the engine for my W108 250S.  This will be the 3rd engine in the car since new.  The first engine lasted 100K miles, I then put in a new factory short block and rebuilt the head. That setup is now worn out at >200K.  Now I'm rebuilding the original block and head. 

I took the block to the machine shop yesterday and showed them the center main bearing that was completely beat, the copper layer was 90% gone and the rest was big flakes that you could pull off.  All the other bearings looked good, no copper showing.  He looked at the journal and it showed evidence that it was oversized from the factory. They will be line bored to correct.

The engine is a M108-I, which was only used in the 250s and a lot of the internals are specific to that model only. It shares some parts with the M114, and much less so with the M129 and M130, all these engines are part of the M189 engine family.

I'm considering using Mobil 1 10-30 oil in the new engine. 

Any thoughts?
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS
'21 E450 Cabrio

daantjie

What grade Rotella have you been using  15W-40?
Daniel
1977 450 SEL 6.9 - Astralsilber

ptashek

I'm using Liqui Moly MoS2 "Leichtlauf" 10W-40 semi-synth in the W124 and W116.
I've tried many others before, from 5W-30 to 20W-50, across a few brands and this one just seems to suit the engines best, despite some initial reservations on the V8 (it just sounded "different").

It uses molybdenum disulfide as a low friction additive, and is really well suited to older engines. If the additive is good enough for highly stressed aircraft engines, it's good enough for an old Benz engine...
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

daantjie

Ja oil talk usually leads to fisticuffs on some forums but I think here on the org we are pretty chill ;D

Much has been written on synthetic oils being "bad" for older engines.  I do not know for sure if this is the case, perhaps clearances on older engines are just bigger and thus thinner oil will leak more?  also seals are older and thus obviously they will leak more nothing to do with the oil in my opinion.  Tons of anecdotal stuff on the interwebs but a lot of that is bullshit honestly.

As long as you stick to a reputable brand and change the oil frequently I think that is most important, along with high levels of zinc in the oil (ZDDP).  I am a big fan of good ol' Castrol GTX, and I run 20W-50 in the 6.9, purrs like a kitty.
Daniel
1977 450 SEL 6.9 - Astralsilber