Refining Economics of Higher Octane Sensitivity, Research Octane Number and Ethanol Content for US Gasoline

Increasing the minimum octane ratings of the U.S. gasoline pool would enable higher engine efficiency in future light-duty vehicles (e.g., through higher compression ratio engines), facilitating greater vehicle fuel economy and lower greenhouse gas emissions. This study applied a linear programming model of the aggregate U.S. refining sector to estimate the technical and economic effects of producing a gasoline pool meeting alternative combinations of national standards for ethanol content, minimum research octane number (RON), and minimum octane sensitivity (OS = RON - MON, where MON is the motor octane number). The primary effects assessed included refining capacity additions and investments, incremental refining and fuel production costs, crude oil consumption, refinery CO2 emissions, and national average gasoline properties and composition. The analysis indicated that (i) with refining technology and gasoline blendstocks currently used in the U.S, the average RON and OS of the gasoline pool could be increased significantly using conventional refining processes and gasoline blendstocks, especially at higher levels of ethanol blending; (ii) a 102 RON standard could be met with E15, E20, and E25; (iii) the highest attainable OS standard would be 10 OS with E10, 12 OS with E15, 13 OS with E20, and 14 OS with E25. While incremental fuel production costs ($/gal) and refining investment requirements ($ billion) would increase with increasing RON and OS standards (for each level of assumed ethanol blending), increased RON for E10 gasoline might be attained at a cost of 3 and 104/gal for 95 and 98 RON, respectively. Adding large volumes of a high-RON, high-OS blendstock, such as ethanol (currently produced in large volume) or iso-octene (currently produced in only de minimis volumes), would extend the achievable RON and OS frontier, with high OS levels achievable only with iso-octene significantly increasing incremental refining cost. Additional ethanol use would offset some of the increase in incremental refining cost by reducing the required volume and RON of the hydrocarbon portion of the gasoline pool.

Automated summary

Increasing the minimum octane ratings of the U.S. gasoline pool has the potential to improve engine efficiency in future light-duty vehicles, leading to greater fuel economy and reduced greenhouse gas emissions. This study analyzed the technical and economic effects of producing a gasoline pool meeting different national standards for ethanol content, minimum research octane number (RON), and minimum octane sensitivity (OS) levels, showing that higher octane levels can be achieved with conventional refining processes and gasoline blendstocks, albeit with increased refining costs. The use of high-RON, high-OS blendstocks like ethanol or iso-octene could further extend the achievable octane and sensitivity levels, although at a higher cost.