honestly, without knowing what the temps were and what they're going up to then down to, anything I say is a guess. with that in mind, the cooling fan comes on at higher temps and will run until it drops to a more normal temp. its not too abnormal to see cooling fans come on regularly this time of year. I live out in the SoCal desert so I run BMW blue
coolant and Water Wetter with about 55 to 60% water. mine doesn't get to the point of turning on the fan (unless I'm using A/C).