Should the Terra use 92 or 95 octane gasoline?

[McAubrey]

According to the official vehicle user manual recommendation, the Terra should use 92 octane gasoline. In addition to checking the appropriate gasoline grade in the vehicle user manual, you can also check the fuel filler cap, which will also indicate the recommended grade. 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 some new technologies, the gasoline grade cannot be solely determined by the compression ratio. High compression ratio engines can also be tuned to use lower octane gasoline 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 Terra occasionally uses the wrong gasoline grade, simply switch back to the correct grade after using it up. 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 increase in octane number will change 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 in real-world driving. For vehicles recommended to use higher octane gasoline, using lower octane gasoline can cause engine knocking. Because the octane number is too low, the gasoline's ignition point decreases and it may ignite prematurely during the compression stroke. If detonation occurs before the spark plug ignites, resistance will appear during the upward stroke. This resistance will cause the engine to run very unstably. If it's only mild knocking, it will just increase noise without significant damage to the engine. However, if obvious knocking is felt, it indicates the engine's condition is already very severe. The vibration not only affects driving stability but can also cause abnormal wear on the pistons and cylinders, and in severe cases, even cylinder scoring.