Motorcycles should use the type of gasoline recommended in the official user manual of the vehicle. In addition to checking the appropriate gasoline grade in the user manual, you can also find this information on the fuel tank cap, which is usually labeled. Typically, the gasoline grade can also be determined based on the engine's compression ratio. For engines with a compression ratio between 8.6-9.9, 92-octane gasoline is recommended; for those between 10.0-11.5, 95-octane gasoline is suitable. If the compression ratio is even higher, 98-octane gasoline should be used. However, with the application of new technologies, the gasoline grade can no longer be solely determined by the compression ratio. Engines with high compression ratios can also be tuned to use lower-octane 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. For example, 92-octane gasoline contains 92% isooctane and 8% n-heptane, while 95-octane gasoline contains 95% isooctane and 5% n-heptane. Occasionally using the wrong gasoline grade only requires switching back to the correct grade after the current tank is used up. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles designed for low-octane gasoline, using a higher-octane grade will not cause damage, but the increase in octane number can alter the fuel's ignition point, leading to delayed combustion in the engine. This results in reduced engine power and thermal efficiency, with the practical effect being poorer performance. For vehicles designed for high-octane gasoline, using a lower-octane grade can cause engine knocking. This happens because the significantly lower octane number reduces the gasoline's ignition point, causing it to ignite prematurely during the compression stroke. If combustion occurs before the spark plug fires, resistance is created during the upward stroke. This resistance makes the engine run very unstably. If the knocking is imperceptible, it may only increase noise without obvious damage to the engine. 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.
