Page "Compression ratio" Paragraph 11

Due to engine knocking ( detonation ), the compression ratio in a gasoline or petrol-powered engine will usually not be much higher than 10: 1, although some production automotive engines built for high-performance from 1955 – 1972 had compression ratios as high as 13. 0: 1, which could run safely on the high-octane leaded gasoline then available.