I don't remember the exact figures, but I do remember being surprised at the heat budget of the typical aircraft engine, specifically, how much heat is removed/dissipated by the engine oil cooler.
Oil has less than one-half the specific-heat of water, and its thermal conductivity is approximately one-fourth that of water, yet a comparatively small oil flow and small oil-cooler can be used to remove a huge amount of heat.

So I started wondering ... Has anyone ever experimented with an engine entirely cooled by engine oil (ie Eliminate the water/glycol radiator completely)?
Is it possible that enough weight could be saved by eliminating "redundant systems" to justify constructing a single large thermally efficient oil-cooler to do-it-all?
The fact that water/glycol systems have been added to air-cooled motorcycles seems to indicate that the answer would be "No", but I still do wonder about it.

Robin Berglund

Here is a heat balance for the rotary.

Paul Lamar Frankfurt