What are the consequences of using 92-octane gasoline in a BMW X3?

[VanIvan]

According to the official vehicle manual recommendation, the BMW X3 should use 95-octane gasoline. In addition to checking the appropriate gasoline grade in the vehicle manual, the BMW X3 can also find this information on the fuel tank cap, which will be clearly marked. Typically, the gasoline grade can also be determined based on the engine's compression ratio. Vehicles with an engine compression ratio between 8.6-9.9 should use 92-octane gasoline, while those with a compression ratio between 10.0-11.5 should use 95-octane gasoline. However, with the application of new technologies, the compression ratio alone cannot determine the appropriate gasoline grade. High compression ratios can also be adjusted to use lower-grade gasoline. This is because, besides the compression ratio, other factors such as ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Generally, the higher the gasoline grade, the higher the octane number and the better the anti-knock performance. 92-octane gasoline contains 92% isooctane and 8% n-heptane, while 95-octane gasoline contains 95% isooctane and 5% n-heptane. If the BMW X3 occasionally uses the wrong gasoline grade, simply switch back to the correct grade after consumption. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended to use lower-grade gasoline, using higher-grade 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 the engine's power output and thermal efficiency will decrease, resulting in poorer performance as experienced by the driver. For vehicles recommended to use higher-grade gasoline, using lower-grade gasoline can cause engine knocking. This is because the significantly lower octane number reduces the gasoline's ignition point, causing premature ignition during the compression stroke. If the fuel ignites before the spark plug fires, resistance will occur during the upward stroke. This resistance makes the engine run very unstably. If the knocking is imperceptible, it only increases noise without obvious engine damage. However, noticeable knocking indicates severe engine conditions, affecting not only driving stability but also causing abnormal wear on pistons and cylinders, and in severe cases, cylinder scoring.