What is the Octane Number Requirement of a Vehicle?
The actual octane requirement of a vehicle is called the Octane Number Requirement (ONR), and is determined by using series of standard octane fuels that can be blends of iso-octane and normal heptane ( primary reference ), or commercial gasolines ( full-boiling reference ). In Europe, delta RON (100C) fuels are also used, but seldom in the USA. The vehicle is tested under a wide range of conditions and loads, using decreasing octane fuels from each series until trace knock is detected. The conditions that require maximum octane are not consistent, but often are full-throttle acceleration from low starting speeds using the highest gear available. They can even be at constant speed conditions, which are usually performed on chassis dynamometers. Engine management systems that adjust the octane requirement may also reduce the power output on low octane fuel, resulting in increased fuel consumption, and adaptive learning systems have to be preconditioned prior to testing. The maximum ONR
