y_p_w said:
Well - I thought about possibilty of contamination. I first
collected the oil in an empty bottle of Chevron 10W-30 motor
oil. I made sure there was only a minute residue of oil left
in the bottle. I really doubt it had anything to do with the
high moly level.
Still - I'm getting the feeling that the letter from SOA saying
that "a certain level of friction is necessary" was incorrect.
Their engineers may want the factory oil to stay in there, but
the SOA letter may not explain the real reason. I've seen a lot
of evidence that moly compounds are used as break-in additives.
One claim is that a high moly level in the oil reduces scuffing
(or "breaking off" of rough surfaces) and promotes a more graceful
deformation (or flattening). Instructions for aftermarket
performance cams recommend that a moly paste be added to the cam
lobes for break-in.
I'm no expert, but I'd guess that there's more than one
break-in mechanism going on. The rings definitely need
a certain kind of metal-to-metal contact with the bores
to seat properly. Call that friction if you like.
On the other hand, you'd want a burnishing action on
the cam lobes and I think the moly paste would be the
best thing to use there.
I'd be willing to bet that the high moly level is due
to assembly lub. I would not be concerned.
Would the sulfur in molybdenum disufide increase copper corrosion?
That COULD be a reason why high amounts of MoS2 might only be used
for break-in unless an engine is spec'ed without copper/brass/
bronze parts. I've heard the new 5W-20 oils for some Ford/Mazda/
Honda cars typically contain high MoS2 levels. Maybe the cars
they've approved for 5W-20 were engineered w/o copper components.
I've had a few motorcycle and car engines apart and
I can't think of any critical parts exposed to lub
oil that are made of copper or copper alloy. Again,
don't lose sleep over it.
