I don't have reliable numbers on this, but rolling resistance appears to be the main factor up to about 60-80km/h, above which drag takes its place. Looking at

I don't have reliable numbers on this, but rolling resistance appears to be the main factor up to about 60-80km/h, above which drag takes its place. Looking at the fuel consumption in my hybrid it's around 50-60% higher at an average speed of 100km/h than at 70km/h. The difference would have been 2x if was just due to drag.