Pat:
20W-50 would have been state of the art in 1974 and was
recommended by the factory.
Times have changed, and technology has moved on. The thinking at
the time was that higher vis oil was needed to compensate for the
thinning that occurs during extended driving. This was thought to reduce
wear by insuring a robust film on moving parts. So far so good.
Since then, the thinking on engine wear is that the vast
majority of wear in fact occurs at startup, when almost all the oil has
drained out of the block into the sump. During extended driving there is
an ample supply of oil, so the impact of viscosity is small. Because of
this change in thinking, engine manufacturers are concerned with getting
oil to the moving parts as quickly as possible at startup, so thinner,
easier to pump oils are recommended. 10W-30 would be a more modern
recommendation, some even recommend 5W-30. Add to this the fact that
there is a small improvement in mileage and HP with lighter oils (less
work to spin the oil pump) and you have a strong consensus to use the
lighter oils.
One other thing to think about; To get an oil to have the
extended viscosity range that 20W-50 has (a spread of 30 points) it is
necessary to add a large quantity of viscositizers. Viscositizers have
inferior lubricating properties, and so degrade the lubricating
properties of the base stock. 10W-30 spans a smaller range of viscosity,
and so uses less viscositizers and therefore has superior lubricity.
This means lower wear despite the lower viscosity.
You will notice a slightly lower oil pressure when the engine is
warm if you switch to 10W-30. Do not be alarmed, as it is to be expected
and does not mean anything is wrong. Quite the contrary, it means better
mileage and more power (not enough for you to notice, though).
Vance
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Pat Leask
Sent: May 23, 2006 5:23 PM
To: 6pack@autox.team.net
Subject: Weight of oil in a TR6?
I've been chatting with a buddy of mine about engine oil weight. It may
sound like a simple question, but what weight oil do you use in a
standard
TR6 motor?
I live in a warm climate and only drive it in the non winters, for all
the
winters we have here <G>. I've been using 20-50 but he said 10-30.
Thanks, Pat
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