Things people say about engines

MythA diesel is just a petrol engine that uses different fuel.

FactUnlike a petrol engine, a diesel engine takes in only air on its intake stroke. Encyclopaedia Britannica: Diesel engine Diesel engines are also called compression-ignition engines, because the fuel is lit by air heated by squeezing, not by a spark. Encyclopaedia Britannica: Diesel engine

MythMost of the fuel in a car goes into moving it.

FactOnly about 12% to 30% of the energy in the fuel you put in a conventional car is used to move it down the road. US Department of Energy and EPA, fueleconomy.gov: Where the energy goes (petrol vehicles) In a petrol car, most of the fuel’s energy is lost in the engine, mainly as heat. US Department of Energy and EPA, fueleconomy.gov: Where the energy goes (petrol vehicles)

MythNikolaus Otto was the first to think of the four-stroke cycle.

FactThe four-stroke cycle was patented in 1862 by the French engineer Alphonse Beau de Rochas. Encyclopaedia Britannica: Nikolaus Otto In 1876 Nikolaus Otto built an engine using the four-stroke cycle; because he was the first to build one, it is called the Otto cycle. Encyclopaedia Britannica: Nikolaus Otto

MythRudolf Diesel always meant his engine to run on oil.

FactRudolf Diesel first planned to run his engine on powdered coal; after his experimental engine was destroyed by an explosion, he turned to liquid petroleum. Encyclopaedia Britannica: Diesel engine

MythEvery engine has pistons going up and down.

FactA Wankel rotary engine has no pistons going up and down: a curved triangular rotor orbits inside a closed casing. Encyclopaedia Britannica: Wankel engine The only moving parts of a Wankel engine are the rotor and the output shaft. Encyclopaedia Britannica: Wankel engine

MythSteam engines are internal-combustion engines.

FactA steam engine is an external-combustion engine: its working fluid does not burn, and it gains energy only by heat passing into it through a heat exchanger. Encyclopaedia Britannica: Internal-combustion engine

MythHorsepower is what an average horse can do all day.

FactJames Watt chose the value of the horsepower in the late 18th century after tests with strong dray horses; it is about 50 percent more than an average horse can keep up all day. Encyclopaedia Britannica: Horsepower

MythElectric starters have always been fitted to cars.

FactCharles Kettering developed the first electric starter, introduced on Cadillacs in 1912. Encyclopaedia Britannica: Charles F. Kettering

MythA hybrid car needs plugging in.

FactA hybrid car has a petrol or diesel engine and one or more electric motors; the battery is charged by regenerative braking and by the engine, not by plugging in. US Department of Energy, Alternative Fuels Data Center: How do hybrid electric cars work?

MythFelix Wankel was a qualified engineer and driver.

FactFelix Wankel, a German engineer, invented the Wankel rotary engine; he never earned an engineering degree or held a driving licence. Encyclopaedia Britannica: Felix Wankel