Octane is the measure of a gasoline's ability to resist knocking, which occurs from uncontrolled combustion in the engine's cylinders. Octane is vital in preventing engine damage. Engines experience prolonged knocking if the gasoline's octane rating is lower than what is required by the engine.
A gasoline's octane rating derives from two testing methods: the motor method and the research method. The motor method runs gasoline through an engine under load, while the research method runs gasoline through a free running engine.
Regular octane is substantial for most cars. However, cars with high compression engines, such as sports cars, luxury cars and older cars, may require gasoline with higher octane ratings.
Your car's engine lets you know if you are using the wrong gasoline. If your engine runs smoothly, switching to a higher-octane gasoline does not prove beneficial.
In addition to the engine's power, the temperature, humidity, engine spark timing and your driving method influence your octane requirements. Accelerating quickly or driving with heavy loads increases your octane requirement. Moreover, hotter and drier air also increases your octane requirement considerably. In turn, higher altitudes decrease your octane requirement. Check your owner's manual to see what your vehicle's octane requirement is.