Yes, the speed of the vehicle affects the consumption of fuel. The main reason behind this is air resistance or air drag. What is this air drag? When you are out for a ride on a cool breezy day, you feel the force of air hitting you in the opposite direction. We can feel the wind in the air around us. Air resistance and air friction are the consequences of this air flow. There is opposition air friction force experience while driving a car. This force is called air drag or air resistance. The car’s motion in turn helps to trounce this force. Thus more fuel is consumed by the car to cut down this air drag.
What is air drag?
Air drag is a mechanical force. It is produced during the interaction between solid body and air. This air drag doesn’t exist in vacuum. Since there are no molecules or anything in vacuum there is no chance for the drag to exist. When the air molecules are pushed away from the path of moving object it leads to a drag. The drag in air is because of the air molecules such as oxygen, nitrogen etc. which have mass. This drag is overcome by thrust. It leads to lift. Lift is a component of aerodynamic force acting opposite to direction of movement of forces. The drain in fuel and fuel efficiency aids to overcome air drag.
How is fuel consumption affected by speed?
Mathematically air drag is proportional to square of its velocity. It becomes like a quadratic dependency. More the speed more is the drag. Whiling away the air around the car takes up to 40% of car’s energy. So traveling with high speed makes it even harder. And car engines have been designed for specific particularities. It would have some thresholds for speed, temperature and rpm ranges. Driving over these ranges will definitely affect the performance of engine.
So if the car has to act for the drag it requires more energy. This energy is gained from the fuel. Thus more the force against air drag more will be the fuel consumed. Hence its always better to have a check on speed of the car in steep regions where there is maximum air drag.