For the same combustion-engine motorcycle in comparable conditions, what generally happens to fuel consumption per kilometre at a high motorway cruising speed compared with a more moderate one?

Correct answer

Fuel consumption per kilometre generally increases.

It generally increases, partly because of greater air resistance. Riding at the maximum permitted speed does not make riding more efficient or safer. Consumption also depends on gear, engine, load, wind, gradient and other factors; it does not increase identically in every situation. Under comparable conditions, higher speed also increases reaction and braking distances.