Should Skyactiv-G engines use 92 or 95 octane gasoline?

[LeJohnny]

According to the official vehicle owner's manual recommendation, Skyactiv-G engines should use 92 octane gasoline. In addition to checking the appropriate gasoline grade in the owner's manual, you can also find this information on the fuel filler cap. The fuel filler cap will clearly indicate the recommended octane rating. Traditionally, the gasoline grade could be determined by the engine's compression ratio: vehicles with compression ratios between 8.6-9.9 should use 92 octane, while those between 10.0-11.5 should use 95 octane. However, with modern technological advancements, compression ratio alone cannot determine the required gasoline grade - high compression ratio engines can still be tuned to use lower octane fuel. This is because other factors also come into play, such as ignition timing, turbocharging technology, and Atkinson cycle technology. Generally speaking, higher octane gasoline contains more octane and has better anti-knock properties. 92 octane gasoline contains 92% isooctane and 8% n-heptane, while 95 octane gasoline contains 95% isooctane and 5% n-heptane. If you occasionally use the wrong octane rating in a Skyactiv-G engine, simply switch back to the correct grade after consumption. However, long-term use of incorrect octane ratings may cause the following issues: For vehicles requiring lower octane: Using higher octane fuel won't cause damage, but the increased octane rating alters the fuel's ignition point, potentially causing delayed combustion. This reduces both engine power output and thermal efficiency, resulting in noticeably poorer performance; For vehicles requiring higher octane: Using lower octane fuel may cause engine knocking. The significantly lower octane rating lowers the fuel's ignition point, potentially causing premature ignition during the compression stroke. If combustion occurs before spark plug ignition during the compression stroke, resistance will occur during the upward stroke. This resistance makes engine operation very unstable. Mild knocking only increases noise without significant engine damage, but noticeable knocking indicates severe engine conditions - the vibrations not only affect driving stability but also cause abnormal wear on pistons and cylinders, potentially leading to cylinder scoring in severe cases.