Fuel consumption is a measurement of the fuel used by an engine in a given time or to power a vehicle over a given distance.

The fuel consumption of a vehicle is measured using three common units:

  • mpg(US) – miles travelled per US gallon
  • mpg(UK) – miles travelled per UK gallon
  • l/100km – litres used per 100km (used in Europe)

Usually fuel consumption is specified for more than one driving environment. For example, in Europe vehicle manufacturers quote three figures:

  • Urban – for city driving
  • Extra-Urban – for out-of-town driving
  • Combined – a mix of Urban and Extra-Urban

Different measurement systems are used in engine testing (and in marine, aircraft and industrial engines). Here, fuel consumption may be measured in gallons or litres per hour. It can also be measured in fuel mass per unit time, for example grams per second (g/s) or kilograms per hour (kg/h).

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Nico Rosberg flat spots a tyre

Flat spot has two automotive meanings, one relating to engine performance and the other to tyres.

An engine flat spot is an operating condition where the engine response is poor. Often the term indicates a point near the middle of the engine speed range where strong and immediate engine response dies away, before returning as the engine accelerates to a higher speed. This kind of flat spot can be caused by poor fuel or ignition mapping, amongst many other factors.

In motor racing, flat spot can refer to tyre damage which is often caused by locking a brake (above). This causes the tyre to wear away in one spot around the circumference. The resulting vibration is uncomfortable for the driver, reduces grip and in extreme cases can lead to suspension failure (as happened to Kimi Raikkonen's McLaren at the German GP in 2005).

A finger follower is a cam follower in the shape of a lever or finger, pivoted at one end. The cam lobe operates on the top of the finger follower, between the pivot and the free end. The valve is operated by the underside of the free end.

Compare rocker.

FCV Fuel Cell Vehicle

FFR Fitted For Radio (military vehicles)

FWD Front Wheel Drive


Fuel injection is a fuel system which injects precisely metered amounts of fuel into an intake system (indirect injection) or directly into the cylinder (direct injection).

Injection systems lend themselves to control by computer, which provides far more precise management of fuelling than is possible using a carburettor.

Injection is a necessity for a practical diesel engine, and on these engines injection has been in use since the 1930s. The first road-going fuel injection system for a petrol car was the 1954 Mercedes-Benz 300SL. Mechanical fuel injection systems became popular on premium and performance cars in the 1970s and took over completely in the 1990s thanks to the standardization of catalytic converters.