Effect of rain and speed on the efficiency...

This morning, we got a heavy downpour. I know already that my effective range is really reduced by more than 20% when it is raining hard. So I turned on the MPGe display to watch closely. My informal observation shows that I got very very bad MPGe <68, when driving at speeds of 35 mph and lower. The slower I get, the worse off the MPGe is on the display. When I go faster, the MPGe increased to about 90, in the heavy rain. The MPGe increased as I drove at 35 to 50 mph, then it starts to go steady from 50-60 mph and starts to go down again after 60 mph.

The MPGe pattern is dramatically different when the road is dry. The optimum speed is at 25 mph when I can get the highest possible MPGe and a bonus of 22% extra range compared to that at 55 mph.

Anyone else observed this?