[Diesel_Dave]

I have a clutched fan (from the factory). It basically doesn't come on until it gets close to overheating. I've run with the whole front grille completely blocked off in 80 deg F temps and never had the fan kick on. That being said, I'm the exception--my diesel runs cool, plus my pulse and glide with my very large engine allows the engine not to get very hot.

I've always thought that a clutched fan was the best option, because it doesn't come on unless you need it, but also doesn't have the conversion losses of a pure electric one (mechanical->electrical->mechanical).