What is an octane rating?
- The measure of an engine fuel’s ability to withstand compression and resist engine knocking.
- Engine knocking occurs when a separate pocket of the engine ignites rather than the air-fuel mixture in the combustion chamber. This will eventually cause damage to the engine and will diminish its overall efficiency.
- More info:
- The octane rating is determined by comparing the fuel of interest’s “anti-knocking” capacity with a mixture of heptane and iso-octane with the same anti-knocking capabilities.
- To determine the octane rating, the percentage of octane in this iso-octane/ heptane mixture is measured. Iso-octane is used because it is known to resist knocking because of its branches, which give it a high activation energy or high amount of energy needed to start combustion.
- Although, octane was used to define the standard, many fuels have comparable anti- knocking capabilities and octane does not need to be in the fuel to have a high octane rating.