This is rough estimating and assumes equal effectiveness of rad and cooler; but you get the idea.

 

Al

 

All Good points except that the oil cooler behind the rad *does* get maximum use out of every CFM of cooling air which is the ideal situation in aircraft.  If it takes a bigger oil cooler, then so be it.  Ever take a look at that 11" stack of heat exchangers in a P51?   That is the biggest reason the plane could escort bombers all the way to & from Germany.  

 

Sorry, I'm going to bore everyone again with my favorite saying on this subject - "Remember, we are trying to build efficient *airplanes*, not efficient radiators."

 

Point taken; but then, lower weight is more efficient, and lower pressure drop can equate to lower drag (efficiency) just as can a smaller amount of air taken on board.  It’s a trade off; and I won’t begin to pretend to know which is best in this case.  I do know that the importance of effective cooling outweighs a bit of airplane efficiency.  (Darn, I knew I should have left out that bit about it being a bad idea:)

 

Al