check this out:
there are three distinct regions.
below 1 - where there's no contact.
between 1 & 2 - where there's contact, but there's decent metal
separation thanks to the oil's hydrodynamic film.
above 2 - where the film gets squeezed through by valve load and there's
direct metal-to-metal wear.
it's this last critical region that's experiencing the most problem.
with sufficient zddp, solid state lubrication prevents serious wear.
back when oil had it as part of its spec, honda cams would look pretty
much the same above #2 as below it.
hardness doesn't prevent wear because it doesn't prevent contact. it
can increase the time to failure, but that's not the point. yes, they
had to go roller. but rollers suck because they increase moving mass.
Parking during the day in a shaded area certainly can extend the life of
headlight lenses, though of course it doesn't solve the inherent problem. My
'04 Accord's lenses are still perfectly clear (as one former US president
used to say) because it has been garaged both at home and at work.
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