Rich had a wonderful explanation of boundary lubrication and the internal
combustion engine. I remember a couple years ago (or decades :-o) when I
was in college the professor explained that even in the enlightened late
20th century, the actual contact/lubrication mechanism that occured at the
piston wall was not well understood. Engines have three basic surface
loading- hydrodynamic (Crank, cam bearings), Sliding with lubrication (cam,
gear contact areas, lifters) and intermittent/boundary lubrication
(pistons/rings primarily but also valve guides). In an engine, which wears
out first is a matter of design, not classification since nearly all can be
designed for near infinite life. Diesel truck run thousands of hours
without major wear but then the engine weighs a ton or so.
Why do MG's eat rod bearings when compared to other engine designs? It
is not because of insufficient film strength or overloading during
accelaration. It is because the size is too small at startup and the metal
to metal contact before oil pressure makes it to the bearings is enough to
wear the surfaces. I am just guessing but I would bet that an Accusump
equipped MG's rod bearings would last forever.
Having said that, the real killer of MG's is inactivity. Sitting allows
the oil to drain out of areas it should be. The first startup after
storage or a long period of inactivity takes more life out of camshafts and
other sliding surfaces than miles and miles of driving- OD or no. I don't
know what the definition of long is but winter storage surely qualifies.
How about from Sunday to Saturday? Our habits of using them for primarily
short pleasure runs doesn't help either.
So, the best thing you can do for your MG is to drive it often and for long
distances. That's almost like the doctor telling you to go home, drink
some beer, and have a cheeseburger! If you can't drive it every day, use
the best oil you can find hoping that it will stick on parts better.
Regards,
Bill Eastman
61 MGA with her Mobil one all migrating to the crank case.
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