Yep, it will save power as the fan takes a fair amount of power to drive. Maybe a couple of horse power.
A viscous fan will help to a point as they only drive sometimes.
I think on something like a Cummins which runs a fan as big as the bonnet on a holden it makes more of a difference. They drag the engine down by about 350 rpm which is a heap on a motor that only revs to 2000 rpm.