I don't know how anyone cannot notice, but when my clutch fan kicks in, there is a substantial and very noticable drop in horsepower - takes away alot of power. Also, my clutch on my fan went bonkers this winter, and locked up. It ran all the the time. Before I sprayed it with penetrating oil, and moved it around by hand to free it up, I had went through 3/4 of a tank of gas. <img src="/forums/images/graemlins/scared.gif" alt="" /> <img src="/forums/images/graemlins/scared.gif" alt="" /> I usually use about a 1/4 tank when I make the same trip! I can't quantify this, in terms of mpg difference, but is was obviously a bunch. I don't know why replacing a plastic clutch fan, with a metal non-clutch fan would offer anyone any benefit.