During the use of a car, many drivers believe that driving slowly helps save fuel. However, this is a misconception and not based on manufacturers’ guidelines.
When purchasing a car, selecting a fuel-efficient vehicle is crucial. However, the way you drive also significantly affects the fuel efficiency of the car. So, how can you drive to achieve the highest fuel efficiency?
In reality, there is no general rule that applies to all types of cars regarding the speed for fuel efficiency. Each car model with its specific technical specifications will have an optimal speed to reduce fuel consumption. Driving too slowly or too fast can both lead to unnecessary fuel consumption.
Why is driving slowly not fuel-efficient?
When driving too slowly, the engine usually operates at low RPM, typically between 1,000 and 3,000 RPM. When the car runs at a low gear, the engine’s revolutions per kilometer will be higher, leading to more fuel consumption for each cycle of rotation.
Moreover, if the car moves at a higher speed, it will shift to a higher gear but still maintain the engine speed within the range of 1,000 to 3,000 RPM. Operating the engine at this RPM range over a long distance will result in less fuel consumption. However, this comes with an increase in air resistance.
Specifically, air resistance increases with the square of the moving speed. For example, when driving at 80 km/h, air resistance is eight times greater than at 40 km/h. This means that when the speed is doubled, air resistance increases fourfold. This implies that the engine has to work harder to overcome air resistance, leading to increased fuel consumption.
To save fuel, drivers should control the speed of the car in the range of 48 to 80 km/h. At this speed, air resistance is not significant, and the engine should be shifted to a higher gear to achieve optimal km/RPM. Unless the car is designed aerodynamically, most cars, when running at speeds between 96 and 104 km/h, will not achieve the optimal fuel economy per km.
Therefore, drivers need to understand that if they drive at a low speed, for example, 16 km/h, over a long distance, it will not actually save fuel compared to driving at a high speed, for example, 144 km/h.
Common mistakes to avoid for fuel-efficient driving:
- Avoid sudden acceleration or deceleration: Do not press the accelerator pedal hard to accelerate quickly and then brake suddenly, as this behavior harms the engine and increases fuel consumption by up to four times.
- Limit excessive air conditioning usage: Do not overuse the air conditioner, especially when the car is moving slowly, as it increases fuel consumption. Experts advise reducing air conditioning usage when the outside temperature is above 26.6 degrees Celsius to save about 10-15% of fuel.
- Refuel when the tank is not empty: To avoid damage to the car, do not let the car run out of gas completely before refueling. The optimal solution is to refuel when the fuel gauge is less than half full.
