Cooling fan - engine - A-series

Hi List,

Strictly talking TRAFFIC AND 30MPH situations, has anyone tried different 
engine driven fans on A-series engines and found a difference in the 
temperature.

NOTE.  I am only interested in traffic and up to 30mph situations because 
above that the fan does nothing to aid cooling.  I am also only interested in 
engine driven fans, not electric fans or both together.

So, any experiences of swapping from a 2 or 4 blade metal fan to the later 6 
blade plastic?  Anyone tried the 6 blade metal?  Anyone tried the 11 blade 
plastic (real cheap over here too)?

Thanks


Daniel1312