| Octane |
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Chemical Formula - \(C_8H_{18}\)
Class/Category - \(IB\)
Boiling Point - \(258.1 F^\circ\)
Flash Point - \(55 F^\circ\)
LFL - \(1.0\)%
UFL - \(6.5\)%
PEL - \(400\;ppm\)
Density - \(0.703\;g/mL\)
Molar Mass - \(114.23\;g/mol\)
Molecular Weight - \(114.23\;g/mol\)
Thermal Conductivity - \(13\;W/mK\)
Liquid Specific Gravity - \(0.703\)
Vapor Specific Gravity - \(3.9\)
Vapor Pressure - \(0.25\;psi\)
Vapor Density - \(3.9\)
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Octane number, also called octane rating, is a measure of a fuel's ability to resist "knocking" or "pinging" during combustion in an internal combustion engine, particularly in gasoline engines. Knocking occurs when the air-fuel mixture in the engine's cylinder ignites prematurely or unevenly, which can lead to inefficient combustion and potential engine damage. The octane number is determined by comparing a fuel's performance to a mixture of two hydrocarbons: iso-octane (which has excellent resistance to knocking and is assigned an octane number of 100) and n-heptane (which knocks easily and is assigned an octane number of 0).
Octane Ratings (U.S.)
Regular Gasoline (87) - This is the standard fuel for most everyday vehicles in the U.S. RON is typically around 91–92, and MON around 82–83.
Mid-grade Gasoline (89) - A step up from regular, used in some vehicles that benefit from slightly higher knock resistance. RON might be around 93–94, MON around 84–85.
Premium Gasoline (91-94) - Common ratings include 91, 92, or 93 (varies by region and brand). Used in high-performance or luxury cars with higher compression engines.
High-Octane Fuels (100 or Higher) - Specialty fuels like 100-octane gasoline are used in aviation, racing, or extreme performance vehicles. Aviation gasoline (avgas) often has ratings like 100LL (low lead), with a RON around 100–104. Racing fuels can go even higher, like 110 or 120, depending on additives and formulation.
