Fuel consumption: How much do high speeds cost?
No speed limit, the left lane is free - and you enjoy it. It goes much faster than the recommended speed of 130 km/h on the highway - and you can watch the fuel needle sink. After a short full-throttle stage, the fuel gauge lights up. Why is that? Read here what speed has to do with the car's fuel consumption and how you can save money.
How does fuel consumption change depending on speed?
Clearly, the faster you drive, the more your car consumes. This is because air resistance increases with increasing speed. It presses against the car, which has to use more force. The engine exerts more effort and therefore consumes more fuel. It should be noted that a streamlined body offers a lower drag coefficient than a less streamlined body.
In the city, the car needs its energy mainly to move the mass of the vehicle, i.e. its weight. In addition, there is the rolling resistance. Air resistance plays a subordinate role at a speed of less than 60 km/h. On country roads and motorways, the situation is different: You can already notice this when you briefly hold your hand out of the side window at 80 km/h.
Air resistance now presses against the front of the vehicle and significantly determines energy consumption. The weight and rolling resistance of the car, on the other hand, play a subordinate role. While rolling resistance remains the same at all speeds, air resistance increases quadratically with speed. From around 80 km/h, the air resistance exceeds the rolling resistance.
At high speeds, all vehicles consume an above-average amount of fuel. High means from around 140 km/h. According to the ADAC, a mid-range car consumes up to two-thirds more fuel if it drives at 160 km/h on the motorway instead of 100 km/h. If you drive your car even faster, the air resistance increases further and the engine needs even more fuel.
So it is the speed that mainly determines consumption. In addition, there are other factors such as the efficiency, the power and the size of the engine. You can achieve the lowest fuel consumption if you drive in the highest possible gear between 60 and 90 km/h, depending on the route.
On motorways, however, low speeds and low revs are less realistic. There you drive fuel-efficiently at a speed between 100 and 130 km/h. But here, too, it depends on the vehicle with engine and transmission. Some cars have nine or ten gears. The last gears are specially designed to be so long that they reduce engine speed and drive very efficiently, thus creating low fuel consumption.
How can you calculate the consumption yourself?
There is, of course, a gasoline consumption speed formula that you can use to calculate the exact fuel consumption. For the exact calculation of fuel consumption, however, you need a lot of technical information such as the exact rolling resistance of the tires, the drag coefficient of the car, frontal area of the car, air density of the environment and all engine characteristics. For everyday use, the exact calculation of fuel consumption at all speeds is therefore likely to be too complicated.
However, fuel consumption can also be roughly calculated as follows: Fuel consumption depends squarely on speed, regardless of the efficiency of the engine. This means that for twice the speed, your car needs four times the power and even eight times the power just to overcome the drag. The size or power of the engine or the distance traveled do not matter. Accordingly, fuel consumption increases exorbitantly.
You can simply name the increased fuel if you assume that you consume more than half as much at 160 km/h than at 100 km/h. With an average consumption of 6.5 liters per 100 kilometers at 100 km/h, at 160 km/h it is already almost 10 liters of fuel per 100 kilometers. So you consume an additional 3.25 liters per 100 kilometers. So the best fuel consumption formula for low fuel consumption is in your own hands: Drive slower, then you burn less fuel and also money.
The formula for average gasoline consumption, regardless of efficiency, is:
Litres refuelled x 100 : kilometres driven = average consumption in litres
Or you can calculate:
(litres : kilometres driven) x 100 = average consumption in litres
You have an electric car: What is the electricity consumption then?
Similar to cars with combustion engines, the energy consumption of an electric car is also increasing. The faster it goes, the more electricity it consumes. Some manufacturers therefore deliberately reduce the top speed of their electric cars at 140 km/h, 160 km/h or 180 km/h.
What options do you have to keep consumption as low as possible?
There are several ways to save fuel. These include, among others:
1. Accelerate gently
2. Choose the highest possible gear
2. Choose narrow tires
3. Set the correct air pressure
4. Disassemble roof racks and roof boxes after use
5. Empty the trunk
6. Avoid short distances
7. Drive with foresight
8. Have your car serviced regularly
9. Calculate average consumption regularly