Avgas

Avgas (aviation gasoline), also known as aviation spirit in the UK, is an aviation fuel used in spark-ignited internal-combustion engines to propel aircraft. Avgas is distinguished from mogas (motor gasoline), which is the everyday gasoline used in motor vehicles and some light aircraft. Unlike mogas, which has been formulated since the 1970s to allow the use of platinum-content catalytic converters for pollution reduction, the most commonly used grade of avgas still contains tetraethyllead (TEL), a toxic substance used to prevent engine knocking (detonation), with ongoing experiments aimed at eventually reducing or eliminating the use of TEL in aviation gasoline.

Turbine and diesel engines are designed to use kerosene-based jet fuel.

The main petroleum component used in blending avgas is alkylate, which is essentially a mixture of various isooctanes. Some refineries also use reformate. All grades of avgas that meet CAN 2-3, 25-M82 have a density of 6.01 lb/U.S. gal at 15 °C, or 0.721 kg/l. (6 lb/U.S. gal is commonly used for weight and balance computation.) Density increases to 6.41 lb/US gallon, or 0.769 kg/l, at -40 °C, and decreases by about 0.1% per 1 °C (1.8 °F) increase in temperature. Avgas has an emission coefficient (or factor) of 18.355 pounds CO₂ per U.S. gallon (2.1994 kg/l) or about 3.05 units of weight CO₂ produced per unit weight of fuel used. Avgas has a lower and more uniform vapor pressure than automotive gasoline so it remains in the liquid state despite the reduced atmospheric pressure at high altitude, thus preventing vapor lock.

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