Where the facts come from
Every factual claim on this site links to its source. This is the full list.
How we checked
We only use expert sources: Encyclopaedia Britannica (its written articles, not its AI summaries or question boxes), the US Department of Energy (fueleconomy.gov and the Alternative Fuels Data Center) and NASA Glenn Research Center. Each fact was written in our own words alongside its source. Our build script stores the source text and, for every fact, checks that the key words and figures really appear in it. 152 of 152 checks passed when this site was last built (3 Nov 2026). Where we couldn’t find one of those sources saying it, we left the claim out.
The charts and games
Our charts, drawings and Inside the Engine use only the facts on this site. The drawings are simplified and not to scale; in the diesel sizes chart the top of each bar is a guide, not a limit. The quiz, sorting, timeline and pairs answers come from the pages below.
All sources (33)
- Encyclopaedia Britannica: Automatic transmission (3 facts)
- Encyclopaedia Britannica: Automobile (9 facts)
- Encyclopaedia Britannica: Cam (2 facts)
- Encyclopaedia Britannica: Carburettor (3 facts)
- Encyclopaedia Britannica: Catalytic converter (2 facts)
- Encyclopaedia Britannica: Charles F. Kettering (2 facts)
- Encyclopaedia Britannica: Diesel engine (22 facts)
- Encyclopaedia Britannica: Differential gear (5 facts)
- Encyclopaedia Britannica: Felix Wankel (3 facts)
- Encyclopaedia Britannica: Flywheel (3 facts)
- Encyclopaedia Britannica: Fuel injection (2 facts)
- Encyclopaedia Britannica: Gasoline engine (19 facts)
- Encyclopaedia Britannica: Gear (5 facts)
- Encyclopaedia Britannica: Gottlieb Daimler (3 facts)
- Encyclopaedia Britannica: Horsepower (5 facts)
- Encyclopaedia Britannica: Ignition system (3 facts)
- Encyclopaedia Britannica: Internal-combustion engine (7 facts)
- Encyclopaedia Britannica: Karl Benz (2 facts)
- Encyclopaedia Britannica: Nikolaus Otto (5 facts)
- Encyclopaedia Britannica: Octane number (2 facts)
- Encyclopaedia Britannica: Rudolf Diesel (4 facts)
- Encyclopaedia Britannica: Sir Dugald Clerk (2 facts)
- Encyclopaedia Britannica: Spark plug (2 facts)
- Encyclopaedia Britannica: Supercharger (3 facts)
- Encyclopaedia Britannica: Wankel engine (4 facts)
- Encyclopaedia Britannica: Wilhelm Maybach (3 facts)
- Encyclopaedia Britannica: Étienne Lenoir (8 facts)
- NASA Glenn Research Center: Engine mechanical operation (4 facts)
- NASA Glenn Research Center: Internal combustion engine (Otto cycle) (3 facts)
- US Department of Energy and EPA, fueleconomy.gov: Where the energy goes (petrol vehicles) (6 facts)
- US Department of Energy, Alternative Fuels Data Center: How do all-electric cars work? (1 fact)
- US Department of Energy, Alternative Fuels Data Center: How do gasoline cars work? (3 facts)
- US Department of Energy, Alternative Fuels Data Center: How do hybrid electric cars work? (2 facts)