How car engines work: the four strokes, petrol and diesel, and the people who invented them.
Suck, squeeze, bang, blow. Here is how the engine under a car’s bonnet turns fuel into motion, why a diesel needs no spark, what the gears are for and who worked it all out, from Lenoir’s gas engine of 1860 to Wankel’s rotary. Every fact is checked against Encyclopaedia Britannica, the US Department of Energy or NASA.
Inside the Engine
Step a piston through the four strokes, intake, compression, power and exhaust, and watch the valves, the spark and the crankshaft. Switch between petrol and diesel to see what changes. Then try Which Stroke? and test yourself.
Inside the Engine is our own code and drawing (simplified, not to scale). Every stroke description is one of the sourced facts on this site; the source shows with each one.
The short version
In an internal-combustion engine the fuel and air burn inside the engine itself, and the hot gases push on a moving surface such as the face of a piston. Encyclopaedia Britannica: Internal-combustion engine
The most common internal-combustion engine is the four-stroke, petrol-powered, spark-ignition engine, thanks to its performance in road transport. Encyclopaedia Britannica: Internal-combustion engine
In a diesel engine, air is squeezed until it is hot enough to set alight the diesel fuel sprayed into the cylinder. Encyclopaedia Britannica: Diesel engine
Explore the engine
The four strokesSuck, squeeze, bang, blow.
Petrol and dieselSpark or squeeze?
Engine partsPlugs, cams, flywheels and more.
Gears and powerTorque, horsepower and the differential.
The pioneersLenoir, Otto, Daimler, Benz, Diesel and Wankel.
Other enginesTwo-strokes, rotaries, hybrids and electric cars.
Myths vs factsIs a diesel just a petrol engine with different fuel?
The big facts pageEvery fact on the site, sourced.
Tile pictures are credited on their pages and on the credits page.
Things to play
- Inside the EngineStep through the four strokes, petrol or diesel, then play Which Stroke?
- Spark or Squeeze?Petrol, diesel or both?
- Engine TimelinePut engine history in order, from 1807 to 1971.
- Engine QuizTen questions at a time, every answer sourced.
- Picture PairsMatch the inventors and their engines.
Found it useful? Help keep this site going.
This site is hand-built, fact-checked and free to use. If Inside the Engine, a game or one of Useless’s notes made you grin, a little support keeps it going and helps the network grow.
Car engine printables
Fact-checked PDFs in A4 and US Letter, sold as instant downloads from the ReallyByte store.
Colour the Engine: Car Engine Colouring Pack
Colour-in drawings of a cylinder, the four strokes, gears, a spark plug, a Wankel rotor and the first engines, each with a fact-checked caption, plus label-the-part pages.
Car Engine Puzzle Pack: Crosswords, Codes & Stroke Logic
A crossword, a word search, a code-cracker, a stroke-order puzzle, a petrol-or-diesel sort and a timeline sort, with answer keys.
Car Engine Fact Cards: Parts, Pioneers & Power
Twenty-four fact-checked cards on engine parts, the four strokes, petrol and diesel, gears and the inventors, ready to cut out.
How an Engine Works: A Car Engine Workbook
Follow the four strokes, compare petrol and diesel, work out gear ratios and horsepower, and build an engine timeline from 1807 to 1971.
Pistons & Sparks: Kids’ Car Engine Worksheets
For ages 7 to 11: name the parts, order the strokes, true or false, spark or squeeze, gear maths and a crankshaft maze.
Car Engine Poster Set
Six fact-checked posters: the four strokes, petrol vs diesel, engine parts, gears, where the energy goes and the engine pioneers.
Best valueThe Complete Car Engine Printables Bundle
All six packs plus a guide, A4 and US Letter, in one download.