Should the VV7 use 92 or 95 octane gasoline?

[DiKayden]

According to the official vehicle manual recommendation, the VV7 should use 92 octane gasoline. In addition to checking the suitable gasoline grade in the vehicle manual, the VV7's fuel cap also indicates the recommended octane rating. Generally, the appropriate 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 required gasoline grade. High compression ratio engines can still be tuned to use lower octane gasoline because other factors, such as ignition timing, turbocharging technology, and Atkinson cycle technology, also play a role. Generally, the higher the gasoline octane rating, the higher the octane value 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 VV7 occasionally uses the wrong gasoline grade, simply switch back to the correct octane rating after the current tank is used up. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended to use lower octane gasoline, using a higher octane rating will not cause damage, but the increased octane value may alter the fuel's ignition point, leading to delayed combustion in the engine. This results in reduced engine power output and thermal efficiency, manifesting as poorer performance. For vehicles recommended to use higher octane gasoline, using a lower octane rating can cause engine knocking. Due to the significantly lower octane value, the gasoline's ignition point decreases, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires during the compression stroke, resistance will arise during the upward stroke. This resistance makes the engine run very unstably. Mild knocking may only increase noise without significant engine damage, but severe knocking indicates serious engine conditions. The vibrations not only affect driving stability but can also cause abnormal wear on the pistons and cylinders, potentially leading to cylinder scoring in severe cases.