Should the MG 5 use 92 or 95 octane gasoline?

[LeoRose]

According to the official vehicle manual recommendation, the MG 5 should use 92 octane gasoline. In addition to checking the appropriate gasoline grade in the vehicle manual, you can also find it marked on the fuel tank cap. Generally, 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 gasoline grade, as high compression ratio engines can also be tuned to use lower octane gasoline. 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 MG 5 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 octane gasoline, using higher octane gasoline will not cause damage, but the increased octane number may alter the fuel's ignition point, leading to delayed combustion in the engine. This results in reduced engine power and thermal efficiency, manifesting as poorer performance. For vehicles recommended to use higher octane gasoline, using lower octane gasoline can cause engine knocking. The significantly lower octane number reduces the fuel's ignition point, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires, resistance will develop during the upward stroke. This resistance leads to unstable engine operation. If the knocking is mild, it may only increase noise without significant 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.