As mine is a race engine, it spends most of it's life in the high RPM bracket, over 6000 RPM. This can cause the viscous coupling to fail. and a failed viscous coupling leads to a fan going bersec in the engine bay, wrecking everything. So for me was primarily preventative, but it gained a coupel HP on the wheels. I popped in an oversize electric fan on the radiator with a thermostat to kick it in at a lower temp.