Standard Test Method for Motor Octane Number of Spark-Ignition Engine Fuel.
Get more information about the standard at ASTM D2700-24b.
ASTM D2700 is a standard test method for determining the Motor Octane Number (MON) of spark-ignition engine fuels, such as gasoline and ethanol blends. The MON is a critical measure of a fuel’s resistance to knocking under higher operating loads and more severe conditions, complementing the Research Octane Number (RON) determined by ASTM D2699. Together, MON and RON help define the fuel’s octane rating, ensuring optimal engine performance and compliance with industry standards.
Details
The Motor Octane Number (MON) is determined using a Cooperative Fuel Research (CFR) engine under specific test conditions that simulate high-speed, high-load engine operations. The test method compares the knocking tendency of a test fuel to that of standard reference fuels composed of iso-octane and n-heptane, which have known octane values.
The MON is typically lower than the RON due to the harsher test conditions, and both values are combined into the Anti-Knock Index (AKI = (RON + MON)/2).
Industries and Applications
ASTM D2700 is widely applied in several industries and applications:
- Automotive industry: Automakers rely on MON values to ensure engines operate efficiently under various driving conditions, including heavy loads and high speeds
- Fuel refineries and distributors: Refiners use this method to certify fuel products, ensuring they meet required octane specifications for market distribution
- Racing and high-performance engines: High-performance vehicles require fuels with high MON ratings to handle extreme conditions without engine knocking
- Regulatory compliance: MON testing is essential for meeting fuel standards set by government agencies to minimize engine damage and improve emissions
- Biofuels: Ethanol and other alternative fuels are tested using ASTM D2700 to ensure compatibility with modern engines and performance standards