The key component in making car wheels move (and ultimately drive the car) is the internal combustion engine. Most cars in use today burn gasoline to power the engine, which in turn moves the car. The entire process can be broken down into several key parts.
The gasoline that you put in your car is derived from crude oil. Once the oil has been mined from the ground, it is taken to a refinery where it is heated and separated into different parts. During heating, the lightest parts of the crude oil that make gasoline are evaporated while the heavier parts sink to the bottom. After further treatment, which includes an additional period of extreme heating, the gasoline is ready to be used in cars.
Once the gasoline is inside the tank, the car's internal combustion engine is used to power the car. It works by drawing gasoline from the tank along a fuel line and into one of its cylinders. Engines differ, but four or six cylinders are usually in each engine. Each one, in sequence, draws in a small amount of gasoline along with a small amount of air before igniting it with a spark from the spark plugs. The small explosion resulting from the fuel burning forces a piston at the bottom of the cylinder downward. This downward motion from each of the cylinders turns the engine's drive-shaft. The remaining gases after combustion of the gasoline are drawn out of the cylinder and pushed from the back of the car as exhaust.
A car's drive shaft is the part that connects the motion of the engine with the wheels. The drive shaft, which on most cars runs the length of the vehicle to the rear wheels, begins to turn as the combustion engine burns gasoline. The turning drive shaft is connected to the rear axle and wheels, which cause them to turn as well, powering the car forward.
Although the wheels would turn without tires, the car probably would not get very far. The tires provide the wheels with grip on the road surface. Without them, the car's wheels would rapidly spin on the road without moving the car forward. Tires are made of a type of rubber that has been hardened to be able to fit around car wheels (rubber is liquid without being hardened first).
Different Types of Engine
Not all cars are powered by internal combustion engines. In recent years electric cars have been the focus of increased attention as an alternative to gasoline-powered vehicles. Their motors or engines are powered by electricity, which provides the power to turn the car's wheels.