I was waiting for IMM to go for that argument... (in the give him enough rope kind of way ;-)
The heat capacity may or may not be an issue. It will depend on if the oil reaches the same temperature as the "hot bits". If it does then Prevost's theory of exchanges would dictate that the oil can experience no further nett gain in heat. In this circumstance the higher SHC oil will allow marginally more heat to be moved (as would a higher flow rate). If however (as I expect to be the case) the oil does not reach the same temperature as the hottest parts of the engine that it comes into contact with then the difference in SHC becomes far less significant.
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