After all this talk of viscosity changes with temp, I plan to put the flowmeter (not arriving until next week) in the cooling loop on the engine.  I'll run the Davies Craig EWP and record the flow rate, then run the engine enough to bring the water up to normal temp, shut the engine off, and check the flow rate again.  I just can't believe this is going to be significantly greater than when cold, but I'll certainly be happy if it is, especially if it will shut Al up :-) 

On the contrary; I’ll be cheering.  I think it’s great that you are willing to make the effort to some data.  We always benefit from good data.

Al