If the majority of light-duty vehicles in the United States ran on higher-octane gasoline, the automotive industry as a whole would reduce its carbon dioxide emissions by 35 million tons per year, saving up to $6 billion in fuel costs, according to a new analysis by MIT researchers.

 

In a study published in the journal Environmental Science & Technology, the team considered a scenario in which fuel is manufactured under a redefined octane rating — the measure of a gasoline’s ability to resist engine knocking during combustion.

 

Currently in the United States, a car’s octane rating is based on the antiknock index (AKI) — a specification for fuel composition that is determined by a standard research octane number (RON) and a motor octane number (MON). The resulting octane ratings for today’s car engines typically range from 87 (regular fuel) to 93 (premium, or high-octane, fuel) — numbers that are commonly displayed at the pump. The higher the octane rating, the more resistant the fuel is to knocking.

 

However, the MIT researchers deemed AKI — and more specifically, MON — to be an outdated measure of engine performance, originally designed to apply to older, carbureted engines rather than modern, fuel-injected engines. To bring the octane rating system up to date, the team considered doing away with MON, and basing engine performance solely on RON.

 

The revised octane rating system would boost the fuel grade of regular gasoline to 93, and premium to 98. The researchers reasoned that the higher fuel grades, while still appropriate for use in today’s engines, could also give oil refiners the opportunity to produce higher-octane fuel, which in turn could spur manufacturers to design vehicles to run on higher-octane — an innovation that could lead to more efficient vehicles.