For a long time, it has been considered that a speed of 90 km/h is optimal for the lowest possible fuel consumption, but a study shows that the most efficient point is closer to 70 km/h.
Fuel consumption depends not only on speed, but also on how the engine operates, the number of revolutions and the gear selected.
In low gears, the engine runs at higher revs and consumes more fuel. According to a study by the French knowledge center Cerema, consumption follows an asymmetrical U-shaped curve. At low speeds, from about 10 to 40 km/h, consumption is relatively high, while as the speed increases it gradually decreases.
The lowest consumption is achieved at around 70 km/h. This is considered the balance point between engine efficiency, travel time and air resistance. After this speed, the advantage starts to disappear.
Air resistance increases significantly and, unlike speed, it increases quadratically. This means that the faster the car moves, the more energy is needed to overcome air resistance.
For example, increasing speed from 100 to 120 km/h can cause about 20 percent more fuel consumption. The effect is even more noticeable in electric vehicles, where higher speed means higher energy consumption and shorter autonomy.
Tests show that the difference between 110 and 130 km/h can mean more than a quarter of additional consumption. Therefore, while driving too slowly is not efficient, driving too fast is not economical either. In conclusion, according to the study data, a speed of around 70 km/h offers a better balance between consumption, engine efficiency and travel time.