Why do high-performance cars generally need high octane gas?

High-octane gas is less likely to ignite prematurely, which can cause knocking or pinging in an engine. Knocking and pinging can damage an engine, so high-performance cars that are designed to run at high speeds and under heavy loads need high-octane gas to prevent these problems.

The octane rating of gasoline measures its resistance to knocking. The higher the octane rating, the more resistant the gasoline is to knocking. Octane ratings are determined by comparing the gasoline to a mixture of isooctane (which has an octane rating of 100) and n-heptane (which has an octane rating of 0). The higher the percentage of isooctane in the mixture, the higher the octane rating of the gasoline.

Most gasoline sold in the United States has an octane rating of 87 or 89. Some high-performance cars require gasoline with an octane rating of 91 or higher. These higher-octane gasolines are typically found at racing fuel stations or specialty gas stations.

Using high-octane gas in a car that does not require it will not improve performance. In fact, it may actually decrease performance by reducing fuel economy and increasing emissions.