I believe electric fans draw something like 25 AMPS. Yours are probably smaller, as you have two, and may draw less AMPS, so the 40 AMP fuse is probably okay. I don't know that I'd run both fans off one relay though. Also unless you control the fans with some sort of thermostatic switch, running them all them time will shorten their life span. Hayden sells a switch that mounts on/through (not in) the radiator. You should be able to pick one up at most auto parts stores. Personally, I'd dump the electric fans and go back to an engine driven clutch fan. At 15 MPG (which is pretty much normal) the electric fans aren't saving you much if anything. Just something else to go wrong.