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Octane Number Requirements of Vehicles at High Altitude
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Abstract
Past tests of vehicles show that their octane number requirements decrease with altitude. As a result, gasoline marketers sell lower-octane-number (ON) gasoline in the mountain states and other high-altitude areas. The current ASTM specifications, which allow reduction of gasoline octane of 1.0 to 1.5 ON per thousand feet, are based on CRC test programs run on 1967 to 1972 model vehicles. However, many new vehicles are now equipped with sophisticated electronic engine systems for control of emissions and improvement of performance and fuel economy at all altitudes. Because these new systems could minimize the altitude effect on octane requirement, Amoco Oil tested twelve 1984-1986 model cars and light trucks. We found their ON requirements were reduced on average about 0.2 ON per thousand feet on an (R+M)/2 basis (RMON/1,000 feet). We expect octane demand on gasoline suppliers in high-altitude areas to increase as these new cars make up a larger part of the vehicle population, and this could raise the cost of gasoline.
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Citation
Callison, J., "Octane Number Requirements of Vehicles at High Altitude," SAE Technical Paper 872160, 1987, https://doi.org/10.4271/872160.Also In
References
- Brooks D. E. “Effect of Altitude on Knock Rating in CFR Engines,” Research Paper RP-1475, Journal of Research of National Bureau of Standards 28 June 1942
- “Effect of Altitude Changes on Octane Number Requirements of Late Model Cars,” CRC Report No. 454 October 1973
- ASTM Standard D 439 Annual ASTM Book of Standards 1987 05 01
- “1977 CRC Altitude Program,” CRC Report No. 500 February 1979
- “1981 CRC Altitude Octane Requirement Program,” December 1981
- “Technique for Determination of Octane Number Requirements of Light Duty Vehicles,” CRC Designation E-15-86 April 1985