The air/fuel ratio is by weight, not volume - so no risk of hydrostatic lockup. But I too have seen the dramatic increase in fuel consumption at cold start. If I reset the trip meter, it reads around 7-8 L/100km after 1 km, then take until 5 km to reach a more modest 5-6 L/100km. To make it really fair you should reset the trip before starting the engine, the start-up itself probably takes a few ml.