What are the effects of filling a car designed for 95-octane gasoline with 92-octane fuel?

[DiVincent]

Filling a car designed for 95-octane gasoline with 92-octane fuel does have effects. If you occasionally use the wrong gasoline grade, simply switch back to the correct grade after consumption. However, long-term use of the wrong gasoline grade can lead to the following impacts: For vehicles designed for lower octane fuel, accidentally using higher octane gasoline will not cause damage, but the increase in octane number will alter the fuel's ignition point, leading to delayed combustion in the engine. This means both the engine's power output and thermal efficiency will decrease, resulting in poorer performance as experienced by the driver. For vehicles designed for higher octane fuel, using lower octane gasoline can cause engine knocking. Due to the significantly lower octane number, the reduced ignition point may cause premature ignition during the compression stroke. If combustion occurs before the spark plug fires, resistance will arise during the upward stroke. This resistance makes the engine run very unstably. Mild knocking only increases noise without obvious engine damage, but noticeable knocking indicates severe engine conditions, affecting not only driving stability but also causing abnormal wear on pistons and cylinders, potentially leading to cylinder scoring in severe cases. Besides checking the recommended gasoline grade in the vehicle's manual, you can also find it on the fuel filler cap. Generally, the gasoline grade can also be determined by the engine's compression ratio: vehicles with compression ratios between 8.6-9.9 should use 92-octane gasoline, while those between 10.0-11.5 should use 95-octane. However, with modern technologies, compression ratio alone cannot determine the appropriate gasoline grade. High compression ratio engines can be tuned to use lower octane fuel because other factors such as ignition timing, turbocharging technology, and Atkinson cycle technology also play roles. Generally, higher octane gasoline has higher octane numbers and 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.