A significant contribution to reducing consumption could be achieved by manufacturers designing their cars to reach normal operating temperature much sooner.

This dramatically increases your chances of it being sunny when the charcoal reaches its correct operating temperature.

This also has the advantage of allowing the engine to reach its optimum operating temperature, so causing less engine wear.

On some older cars, thermostatically controlled radiator slats restricted air flow to the radiator matrix until normal operating temperature had been reached.

In this way, the aircraft's engine would be at or near normal operating temperature immediately upon getting airborne.