Correct Datatec, they run a lot quieter and they do save you fuel. I ran my diesel P38 manual for four years without problems including off road lamping etc. I don't remember what it origionally cost, but it was an easy fit, but make sure you squeeze it well up to the corner of the rad when fitting so theres lots of clearance if the engine moves about.
I could get a genuine 30mpg if I didn't exceed 65mph. Compared to 3/4 mpg less with the unnecessary viscous fan (for moderate use) it would take a halfwit to ignore the saving.