Why Octane Matters

“Knock Three Times” is a song you may turn up on the radio but while you sing this oldie but goodie, you don’t want there to be a knock in your engine. Octane, represented by the numbers on the buttons at the gas station is what keeps your engine from knocking. The higher the octane number, the better your engine runs.

Efficiency is why octane matters. Octane helps prevent the air/fuel mixture in your engine from detonating prematurely causing a knock or pinging noise under high load. Back in the day, you would actually hear a knock under the hood but today with modern technology, a vehicle’s computer can adjust its ignition timing to reduce and eliminate knock. This is important because when there is engine knock, it reduces mileage and raises your cost per mile for a gallon of gas.

On average, regular gasoline today has an octane rating of 87, midgrade 89 and premium 91. Usually, the higher the octane number, the higher the cost of fuel. However, higher octane fuel often costs less when ethanol is used to boost octane. Ethanol is one of two readily available octane sources. It is plant based, locally made and cleaner than the other octane source, toxic aromatic hydrocarbons such as benzene created at an oil refinery. Almost all of the 87 octane regular gasoline sold in the United State as 10% ethanol in it. The higher octane fuels such as 89 and 91 are usually created with toxic aromatic hydrocarbons but ethanol is the cleaner octane option.

When ethanol is added to fuel, it replaces the toxic aromatic hydrocarbons, not only boosting octane but also significantly reducing the carbon content of fuel. With so much talk about reducing carbon emissions across the transportation sector, a nationwide transition to a higher octane fuel using ethanol would help reduce carbon emissions for millions of cars on the road today, improving engine efficiency and saving consumers money.