1985 Mercedes 300D OM617, Valvoline Blue 10w30 @ 5K mi.

[Alex_V]

Second run of a 10w30 in this engine, continuing to debunk the fear of 30 weights and thin 40 weights in these engines. Other columns (L to R) are Schaeffer's 5/40, M1 euro 0/40, Schaeffer's 5/40 in my other 617, and T5 10/30.

 

[wpod]

What is the blacked out column? How would a uoa tell the viscosity isn't damaging the engine?

 

[loneryder]

Do diesel engines shed more iron than gas engines?

 

[Alex_V]

What is the blacked out column? How would a uoa tell the viscosity isn't damaging the engine?

The fear of a thinner oil is that it doesn't keep a good enough oil film between the parts to prevent metal/metal contact. That the wear numbers are so consistent between high-quality 5W40's and the 30 weights indicates that's not a concern in this engine.

The blacked out column is an old sample from a failed engine I grabbed by mistake, but haven't had them take out of my files(?) yet.