Everyone who has been to the gas pumps knows about different fuel grades. Typically 87, 89, 91, and sometimes 93. You may even know that the numbers correspond to the fuels’ octane rating – but what is octane, and why is a higher number usually perceived as better?

The octane rating we see on pumps is a grading the gasoline has in relation to its resistance to detonation. The higher an octane number, the more stable the gasoline is. Your vehicle’s engine is designed to burn gasoline in each of its cylinder with controlled combustion – utilizing spark plugs for gasoline-powered cars, and relatively higher pressure without spark plugs for diesel-powered cars. As an engine increases in RPM or compression, the gases in the combustion chamber increase in temperature. At a certain point, they can become so hot they ignite earlier than is needed and can cause detonation or auto-ignition. If this occurs, it acts as an opposing force that pushes opposite of your engine’s rotation, which can cause knock or eventual catastrophic failure.

Many carmakers now make their engines with forms of forced induction, such as turbochargers. This along with more precisely-built performance engines can have higher demands for their overall operation (read: combustion). Hence why some carmakers recommend or flat-out require drivers to use higher-rated octanes – both for reliable operation and better performance.