Knock Perception- A 1975 Customer/ Rater Study by CRC

Octane requirements of late model vehicles were determined by trained knock raters and compared with those determined by customers.

Average differences of independent distributions of customer and rater requirements were about 3 Research Octane Numbers/2 Motor Octane Numbers at part-throttle and 6 RON/4 MON at full-throttle and maximum octane requirement conditions.

Five percent of the customers objected to knock when their cars were operated on fuel matching rater requirements, while 50 percent objected when using fuel 6 RON/4 MON lower.

Another program is planned because differences between rater and customer octane requirements were greater than expected.