Today, the Sabin Center published a new working paper discussing the possibility of federal and/or state regulation to increase fuel octane levels. Many readers may be wondering: what is octane? And why do we want to increase it? In simple terms, octane is a measure of a fuel’s ability to withstand compression in a vehicle engine, without self-igniting. Most fuel sold in the U.S. has a low octane rating, meaning that it is prone to self-ignition when compressed, and thus can only be used in low-compression engines. Those engines are extremely inefficient and emit significant carbon dioxide. It’s not surprising then that transportation is the second largest source of carbon dioxide in the U.S., accounting for a massive 31 percent of national emissions in 2014 according to the Environmental Protection Agency (“EPA”).
Carbon dioxide emissions could be reduced by increasing engine compression ratios. In high compression ratio engines, fuel is subjected to greater pressure in the combustion chamber and therefore burns more completely, producing more power with fewer emissions. Despite these benefits, however, high compression engines are not widely used in the U.S. This is primarily due to concerns over the potential for high compression engines to experience knock, an abnormal combustion phenomenon wherein fuel self-ignites and explodes, resulting in an increase in pressure which can damage the engine and reduce vehicle efficiency. To avoid knock, high compression engines must use premium, high octane fuel. A 2014 study by researchers at the Massachusetts Institute of Technology found that switching to premium fuel would enable the deployment of high compression engines which are 2 to 5 percent more fuel efficient than current models.