"JAXAshby" wrote
Listen to an engine upon startup with heavy oil in it (even at summertime
temps) and hear all the grinding and banging and clattering going on
inside the
engine for the first ten or fifteen seconds, let the engine warm up a
couple of
minutes, shut it off, restart and listen again.

If you can't hear the difference, replace the battery in the hearing aid.

JAX is right.

Some 'Shovel Head' H-D owners had to redo their top ends every season,
sometimes more often up north. Turned out the problem was that "everybody"
knew that heavier oil was best and some even used 70 wt. Had to to get the
oil pressure in their roller-bearing Hogs up to that found in a plain
bearing Chevy! Of course it took an hour to get oil up the tiny tubes
feeding the valve rockers - oil which incidentally helped cool the head and
valves. H-D spent mucho $$ developing a multigrade to solve the problem but
"everybody" knew they didn't give enough oil pressure. Minnesota boy I know
rebuilt 7 times in 5 years then went to H-Ds multigrade and last I heard
hadn't had to rebuild in 10 year.

The only problem with using multigrade oils in some older engines is their
detergent capabilities. With few exceptions they are designed to trap and
hold dirt til it can be removed by our wonderful full-flow filters. That's
one of the reasons motors are lasting 200,000 and more miles longer than
they did in the '50s. But what if your or BSA or Triumph or Atomic-4 don't
have a full flow filter? Well then get nondetergent multigrades from Morris
in England.