`The problem with this is that the oil is essentially stagnant in the pan'

Al, this is only 'cause you haven't looked inside when its running - there's
an oil pump driving this stuff round the engine all the time, it just starts
and finishes at the bottom of the oil pan.  The flow rate will be the same
as anywhere else on the system that you would choose to oil/air cooler.  Its
true that the `dwell time' in the oil pan will be longer as this is your
reservoir but this is a good thing.

One can discuss the merits of a (hot) water to (hotter) oil heat exchanger,
but that's a different question and one where I have no experience.  They
are used on cars a lot but I don't know about their efficiency for
continuous high power operation.


Mike
Nice moose Kevin