A fuel’s octane rating is a measure of its ability to resist “knocking” or “pinging,” which is caused by the air/fuel mixture detonating prematurely during combustion in the engine. According to the Department of Energy, “using a lower octane fuel than required can cause the engine to run poorly and can damage the engine and emissions control system over time. It may also void your warranty.”  These vehicles will have poorer performance, reduced fuel efficiency and increased greenhouse gas production on lower octane fuels.


Ethanol’s Octane Benefit

Most of the benefits associated with using ethanol – from reducing petroleum imports to decreasing greenhouse gas emissions – are well known.  However, one of ethanol’s most important benefits is also one of its best kept secrets: octane.

With a blending octane rating of 113, ethanol offers more engine knock resistance at a lower cost and cleaner than any other gasoline additive available.  In the past, gasoline refiners produced all of the octane they needed from petroleum hydrocarbons. But refinery processes to increase octane production are energy intensive and costly.  As ethanol availability has grown, refiners have optimized their operations to reduce hydrocarbon octane production and take advantage of ethanol’s superior clean octane properties.

Most refiners today produce gasoline blendstock with an octane rating of 83 or 84, and upgrade it to 87 (the minimum allowed in most states) by adding 10% ethanol. This offers significant cost savings and reduced energy use and emissions at the refinery.

Ethanol’s role as an octane source has an even brighter future. Demand for higher-octane gasoline is growing, as automakers are introducing more vehicles that require or recommend the use of premium. A high-octane, mid-level ethanol blend like E20-E40 can deliver the same – or better – fuel economy as regular gasoline when paired with an optimized engine, but with less energy expended per mile and far fewer emissions. That’s why many automakers view ethanol-based high-octane fuels as a winning strategy for compliance with future fuel economy and emissions standards.

Not only is ethanol the lowest-cost octane source, it is also the cleanest and safest option available. Hydrocarbon octane sources such as MTBE and aromatics like benzene are highly toxic and pose great risk to our air and water.