[b][/b] I had an electric fan on it, but when the weather got warm it wouldn't keep it cool. SO, I put the engine driven fan back on it. I LOST ABOUT 1 MPG. Plus the fact that the electric fan doesn't run continuously keeps the load off the alternator except when the fan comes on. I had it set up on a thermostat. the horsepower loss is noticeable too. Those factory fans and clutch is heavy!