Octane Ratings

Our Campaigns

The Energy Future Coalition’s strength is its ability to bring together diverse stakeholder groups to effect meaningful change in the energy sector. From its inception, the Coalition has built successful partnerships to promote clean energy, developed innovative business approaches to reduce greenhouse gas emissions, and promoted high-level stakeholder engagement in the clean energy sector, as described further below.

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.