notice the power is expressed in kilowatts, not horsepower

In the 1500 to 2000 rpm highway cruise situation, power consumed by a typical fan from the engine is very low

In the footnotes to the above graph, the author writes that he used information from SAE papers on both the Dodge 340 V8 and the Chevrolet 350 V8.

Unlocked a 1995 Ram viscous clutch is allowing the fan to run at 880 rpm when the engine is turning 1750 rpm

Automobile fan power consumption is hard to find,
but the air conditioning replacement company Lau-Conaire has horsepower consumption numbers for many, many fan designs similar to automobile fans, by rpm, and by number of blades.