Pump gas and most race gasoline is rated in the (R+M)/2 fashion, which refers to an average of two ways that octane is measured: Research and Motor octane. Research octane uses an industry-standard, single-cylinder test engine run at 600 rpm with an inlet-air temperature of 100 degrees Fahrenheit. Motor octane numbers are generated with this same test engine operating at 900 rpm with inlet air at 300 degrees F. Typically, Research octane numbers are 8 to 10 numbers higher than Motor octane numbers, since higher inlet air temperatures will increase an engine’s tendency to detonate. There is an almost infinite number of ways to create the (R+M)/2 octane rating. According to Wusz, higher Research numbers will reduce part-throttle detonation, while higher Motor numbers are better for detonation resistance at wide-open throttle.