In a combustion-engine car starting with a cold engine, on which journey does the warm-up phase have a greater effect on average fuel consumption per kilometre?

Correct answer

On very short trips starting with a cold engine.

On very short trips, because more of the journey takes place before normal operating temperature is reached. Average fuel consumption per kilometre can be higher than in comparable conditions with a warm engine; a short journey does not necessarily use more total fuel than a long one. A cold catalytic converter treats some pollutants less effectively, but should not be presented as the main cause of increased fuel consumption. Drive smoothly and follow the manufacturer’s instructions; avoid unnecessary revving or idling to warm a cold engine.