Gene,
Hydrodynamic lubrication takes place regardless of the type of oil used. In the case of a plain
bearing such as those used on the crankshaft, there are conditions when boundary layer lubrication is
present such as upon start up. After the crank picks up speed, a wedge shaped film of oil is present
that is created by the hydrodynamic forces. At this point, their is full film lubrication. The
additives you mention do not change this. If their never existed a boundary layer condition, there
would never be any bearing or journal wear and the bearings would last indefinitely. Whether you use
conventional or synthetic, this is not the case. Crusader Marine Engines did a study on this a few
years ago and came to the conclusion that, under normal operating conditions, there was no benefit to
using synthetics in their engines.

Gene Kearns wrote:

On Fri, 19 Dec 2003 01:34:58 GMT, Jim Kelly wrote:

I think you are getting your balls in a bunch. You are confusing extreme
pressure properties of certain types of lubricants with the ability of both
synthetic and conventional oils to operate satisfactorily in the typical
boundary layer lubrication environment of an internal combustion engine. You
need to read up on tribology and the mechanics of an oil film in plain bearing
applications as well as sliding motion applications. The most detrimental
aspect of lubrication in an internal combustion engine is contamination from the
combustion process. Unlike a gear box application, the oil in an engine is
subject to the byproducts of the combustion process as well as unburnt fuel.
For this reason, changing the oil and filter on a regular basis is much more
important than the type of oil used.




Jim,

Your confusion seems to be in relying on the boundary layer type of
lubrication. Modern synthetic lubrication relies on hydrodynamic
lubrication. Boundary layer lubrication is handled by tri phenyl
phosphate or (of late) tricresyl phosphate and is a last resort.

Use synthetic lubricants and metal-to-metal contact, most likely,
won't be an issue.

--

Grady-White Gulfstream, out of Southport, NC.

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