Subject: 40W oil causing wear problems over 30w?
From:

Hell, multi weight oils start out at their low number and get more viscous
as
their temp rises.

no they don't. 15W-40 is the same viscosity ("thickness" if you will) at
"room
temp" as straight 15W oil is, and the same viscousity as 40W at engine
operating temperature. 15W-40 is much more viscous at room temp than it is
at
engine operating temp. If you doubt that pull the dipstick on a warm engine
and see.

Perhaps I misstated. Multi weights oils, as I understand, when they get hot
only thin out to the point that their high weight number would at the same
temp.
Something about polymers uncoiling into long chains.

In other words think of a 15-40W oil as a 15W oil that will not thin more than
a 40W would when hot.

Like I said, that's my understanding. But, I could be wrong. That's why I asked
the question. :-)

Capt. Bill

Perhaps I misstated. Multi weights oils, as I understand, when they get hot
only thin out to the point that their high weight number would at the same
temp.
Something about polymers uncoiling into long chains.

In other words think of a 15-40W oil as a 15W oil that will not thin more
than
a 40W would when hot.

Like I said, that's my understanding. But, I could be wrong. That's why I
asked
the question. :-)

Capt. Bill

That is correct.