The idea
Beginner explanation — switch to Technical for the engineering detail.
A car is a machine for turning stored energy into controlled movement. Petrol and diesel hold chemical energy; an engine burns the fuel and turns some of that energy into a spinning crankshaft. An electric car stores energy in a battery and a motor spins instead.
The spinning output is rarely at the right speed for the wheels, so a gearbox trades speed for turning force. A propshaft or driveshafts carry the rotation to the wheels, and a differential lets the left and right wheels turn at different speeds in corners. Finally the tyres grip the road and push the car along.
Around that power chain sit systems that keep it alive (cooling, lubrication, the electrical system) and systems that let you control it (steering, brakes and suspension). Everything is held together by the body and chassis.
What you will learn
- Trace the path of energy from fuel or battery to the road
- Name the job of the engine, transmission, driveline and tyres in that chain
- Distinguish the power chain from the supporting systems (cooling, lubrication, electrics) and the control systems (steering, brakes, suspension)
- Explain why most of the energy in fuel never reaches the wheels
How it flows
Read the diagram as text
- Fuel or battery → Engine / motor (fuel / current)
- Engine / motor → Transmission (torque at engine speed)
- Transmission → Driveline & differential (multiplied torque)
- Driveline & differential → Tyres (wheel torque)
- Fuel or battery: Stored chemical or electrochemical energy
- Engine / motor: Converts energy into crankshaft rotation
- Transmission: Trades speed for torque
- Driveline & differential: Carries torque to the driven wheels
- Tyres: Turn wheel torque into thrust at the road
Step by step
Read each step in order.
Step 1: Energy is stored on board
Fuel in the tank or charge in a battery is the car's energy supply. Everything the car does is paid for from this store.
Step 2: The engine or motor makes it spin
The engine burns fuel to push pistons that turn a crankshaft. An electric motor uses magnetic forces to turn its shaft directly.
Step 3: The gearbox matches speed and force
Low gears give strong pulling force for starting off; high gears let the engine turn slowly at motorway speeds.
Step 4: The driveline delivers drive to the wheels
Shafts carry the rotation to the driven wheels, and the differential lets the outside wheel spin faster than the inside one in a turn.
Step 5: Tyres turn torque into thrust
The tyre's grip on the road is what actually pushes the car forward, turns it and stops it.
Go deeper
Optional. Open a panel for the engineering detail — or switch to Technical above.
The engineering explanation3
Treat the vehicle as an energy-conversion chain. Chemical energy in fuel (about 43–45 MJ/kg for petrol and diesel) is released by combustion, and the engine's thermodynamic cycle converts a fraction of it into shaft work. In everyday driving a petrol car delivers very roughly a fifth to a third of the fuel's energy to the wheels; the rest leaves as heat through the exhaust and cooling system, plus pumping, friction and accessory losses.
The engine produces torque over a limited speed band, so the transmission selects a ratio that matches engine speed to road speed. Wheel torque is engine torque multiplied by the gear and final-drive ratios (less driveline losses), and tractive force is that wheel torque divided by the tyre's rolling radius. The car accelerates when tractive force exceeds the road load: aerodynamic drag, rolling resistance and any gradient.
The control systems shape the forces at the four contact patches. Brakes convert kinetic energy (½mv²) into heat, steering sets the tyres' slip angles to generate cornering force, and suspension keeps the tyres loaded consistently over bumps. Supporting systems maintain the operating conditions: lubrication separates moving surfaces, cooling holds metal temperatures in a safe window, and the electrical system powers ignition, injection, sensors and control units.
Key concepts4
- Powertrain
- Everything that creates and delivers drive: engine or motor, transmission, driveshafts, differential.
- Tractive force
- The forward push the driven tyres exert on the road.
F = T_wheel / r- Road load
- The forces resisting motion: aerodynamic drag, rolling resistance and gradient. Surplus tractive force accelerates the car.
- Kinetic energy
- Energy of motion that the brakes must turn into heat to stop the car.
E = ½ m v²
Common misconceptions3
MythThe engine pushes the car directly.
RealityThe engine only spins a shaft. The forward push comes from the tyres reacting against the road surface.
MythMost of the fuel's energy moves the car.
RealityIn typical driving most of it leaves as heat through the exhaust and radiator; only a minority reaches the wheels.
MythBrakes and steering are separate from the drivetrain's physics.
RealityAll of them work through the same four tyre contact patches, which share a limited amount of grip.
In the real world3
- A warm radiator and hot exhaust after a drive are the unused energy from the fuel made visible.
- Pulling away in third gear feels sluggish because the gearbox is multiplying the engine's torque less than first gear does.
- On ice the engine and gearbox work exactly as usual, but the tyres cannot pass the force to the road, so the wheels spin.
Common questions
Short answers to the questions people most often ask about this topic.
How does a car work, in simple terms?
An engine or electric motor turns stored energy into rotation. The transmission adjusts that rotation's speed and torque, the driveline carries it to the driven wheels, and the tyres push against the road. Brakes, steering and suspension control where the car goes and keep the tyres gripping.
What are the main systems of a car?
The powertrain (engine or motor, transmission and driveline) makes and delivers drive; the chassis systems (brakes, steering, suspension, wheels and tyres) control the car; and the electrical, cooling, fuel and climate systems support everything else.
Where does the energy in a car's fuel go?
In a petrol car much of the fuel's energy leaves as heat through the exhaust and cooling system; only part becomes work at the crankshaft. That work overcomes air resistance, tyre rolling resistance and friction, and the brakes turn the car's kinetic energy into heat when it slows.
Check your understanding
3 questions. Your best score is saved in this browser.
0 of 3 answered
Question 1 of 3
What ultimately pushes a car forward?
The story behind it
Who worked this out, and what they were up against. Optional.
1888
Bertha Benz
Wife of Carl Benz; driver of the 1888 trip
Proved a motor car could make a long trip, and told its maker what to fix.
On 5 August 1888 Bertha Benz drove from Mannheim to Pforzheim, about 106 km, with her sons Richard and Eugen, without telling her husband and without official permission. Officially she was visiting her mother; her real aim was to show Carl that the car could succeed commercially once the public saw it was useful. Ligroin, the solvent the car needed, was sold only by chemists, so she bought it at the pharmacy in Wiesloch. She cleared a blocked fuel line with her hatpin and used her garter as insulation, and afterwards suggested brake linings and an extra gear for hills.
Worth knowing: The source credits Carl Benz, not Bertha, with having a cobbler install leather brake linings.
Sources
Retold in our own words from the sources above.
Almost there
- Overview — Read the introduction to the end.
- See it work — 5 steps left to read
- Go deeper (optional) — Optional: open a deeper panel or switch to Technical.
- Check — Answer the quiz questions.
- Story (optional) — Optional: who worked this out?
Progress is stored only in this browser — there is no account.
Sources & attribution
Further reading
- The engineHow a Car Works · consulted 2026-10-21(external site, opens in a new tab)
Further reading on an external site. Linked only; AutoVerse lesson text is written independently.
- How the transmission worksHow a Car Works · consulted 2026-10-21(external site, opens in a new tab)
Further reading on an external site. Linked only; AutoVerse lesson text is written independently.
- Licence
- AutoVerse original content
This lesson is original AutoVerse writing. The links above are suggestions for further reading, not the source of this text.