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The mixture known as gasoline or petrol, when used in high compression internal combustion engines, has a tendency to knock (also called "pinging" or "pinking") and/or to ignite early before the correctly timed spark occurs (pre-ignition, refer to engine knocking).
In the U.S. MTBE has been used in gasoline at low levels since 1979, replacing tetraethyllead (TEL) as an antiknock (octane rating) additive to prevent engine knocking. [19] Oxygenates also help gasoline burn more completely, reducing tailpipe emissions. Oxygenates also dilute or displace gasoline components such as aromatics (e.g., benzene ...
The octane rating of gasoline is measured in a test engine and is defined by comparison with the mixture of 2,2,4-trimethylpentane (iso-octane) and normal heptane that would have the same anti-knocking capability as the fuel under test. The percentage, by volume, of 2,2,4-trimethylpentane in that mixture is the octane number of the fuel.
A gasoline-fuelled reciprocating engine requires fuel of sufficient octane rating to prevent uncontrolled combustion (preignition and detonation). [9] Antiknock agents allow the use of higher compression ratios for greater efficiency [ 22 ] and peak power . [ 23 ]
Fuel additives in the United States are regulated under section 211 of the Clean Air Act (as amended in January 1995). The Environmental Protection Agency (EPA) requires the registration of all fuel additives which are commercially distributed for use in highway motor vehicles in the United States, [8] and may require testing and ban harmful additives.
Although initially marketed in 1958 as a smoke suppressant for gas turbines, MMT was further developed as an octane enhancer in 1974. When the United States Environmental Protection Agency (EPA) ordered the phase out of TEL in gasoline in 1973, new fuel additives were sought. TEL has been used in certain countries as an additive to increase the ...
The fuel-characteristics of a particular gasoline-blend, which will resist igniting too early are measured as the octane rating of the fuel blend. Gasoline blends with stable octane ratings are produced in several fuel-grades for various types of motors. A low octane rated fuel may cause engine knocking and reduced efficiency in reciprocating ...
When used as a test fuel component in anti-knock test engines, a 100% heptane fuel is the zero point of the octane rating scale (the 100 point is 100% iso-octane). Octane number equates to the anti-knock qualities of a comparison mixture of heptane and iso-octane which is expressed as the percentage of iso-octane in heptane, and is listed on ...