Can Lower Octane Fuels Be Used in Cars Requiring Premium Fuel?

Heed the owner's manual's instructions about fuel octane.

A fuel's octane rating refers to the ratio between the two substances that comprise the gasoline. Especially since gasolines with different octanes do not seem different upon casual observation, it can be tempting to always choose the least expensive fuel.

Octane Ratings

The numbers on the buttons at the gas pump are the octane ratings for each fuel. Higher octane fuels can be compressed more before igniting, a property that can be used to generate more power.

Below Recommended Octane Rating

High-performance cars, like those with superchargers or turbochargers, compress the air fuel mixture to a higher pressure than most vehicles do. These engines typically require fuel with higher octane ratings, because lower octane fuel is more likely to prematurely ignite itself when put under such pressure. This premature ignition, called engine knock, reduces engine efficiency and can damage the pistons. Always follow your owner's manual's recommendation for fuel type.

Above Recommended Octane Rating

Using higher octane fuel offers no benefit in performance or fuel efficiency unless your vehicle was designed to use it. Most engines compress the air fuel mixture only to a level that is safe when used with standard octane fuel. If your owner's manual suggests using standard octane fuel, your vehicle's engine will not be able to make use of the extra potential of premium fuel.

References

• Wanderings: Is High Octance Gas Worth the Money?
• AA1 Car: Fuel Octane Ratings