Engine oil recommendations, -75 Mercedes 450 SEL

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Apr 21, 2009
I would be happy for recommondations for engine oil for my old Benz. It's a 4,5 litre V8 with SOHC with manually adjusted lifters (no rollers).

When I bought it the engine was extremely dirty inside with a 2 mm sticky soot/oil layer almost every where. I cleaned out as much as I could and have now driven it for about 300 miles with a 15w/40 semi synthetic (SL) oil to clean out some of the dirt.
I'm going to change oil soon and I'm confused what to look for. Zink?
In the manual they recommend for my cold climate "15w-40, 15w-50, 10w-40 and 10w-50 (multigrade)"

First, make sure you PCV [positive crankcase ventilation] system is perfect.
Then use any of the oils you mentioned.
The lower the first number in oil viscosity designations, the easier the starting will be.
Therefore, a 5-40 would be expensive, but the best '40' choice.
Using an HDEO 15W-40 with 5K OCI's will never lessen the almost 500K mile expected life of the bottom end of these V8's.

Top end needs to be inspected and timing chain, tensioners, guides, etc. monitored for stretch and wear, oiling system plastic parts get brittle and need replacing, etc.

A good modern 15W-40 oil goes a long way in these engines!

Good Luck!
I read this on acccc.net :
"Another concern with older engines is PAO oil's effect on internal components made from Polyoxymethylene plastic (aka Dupont Delrin). PAO oils can potentially cause stress cracking of plastic engine parts made from this plastic. A Group III oil may be a better choice in engines having internal Delrin plastic parts."

I changed most of the plastic chain guides, one was actually broken. I don't want them to brake again.

Here in Sweden they sell "semi synthetic" 15w-40 oil. Is that better than fully synthetic considering the plastic parts?
Does HDEO mean Diesel motor oil?
HDEO = H(eavy) D(uty) E(ngine) O(il)

Typically they 15W-40, 5W-40 and some 40W, 30W or 10W-30 oils...

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