Should Volkswagen Use 92 or 95 Octane Gasoline?

[Allison]

According to the official vehicle manual recommendations, most Volkswagen models should use 95 octane gasoline. However, the entire 2021 Bora 1.5L series and the 2022 Polo Plus models should use 92 octane gasoline. In addition to checking the appropriate gasoline grade in the vehicle manual, Volkswagen owners 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. Vehicles with a 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 engines can also 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 number, 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 a Volkswagen occasionally uses the wrong gasoline grade, simply switching back to the correct grade after consumption is sufficient. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended for lower-octane gasoline, using higher-octane gasoline will not cause damage, but the increased octane value may alter the fuel's ignition point, leading to delayed combustion in the engine. This reduces the engine's power output and thermal efficiency, resulting in poorer performance. For vehicles recommended for higher-octane gasoline, using lower-octane gasoline can cause engine knocking. The significantly lower octane value lowers the fuel's ignition point, causing premature ignition during the compression stroke. If combustion occurs before the spark plug ignites, resistance will develop during the upward stroke, making the engine run very unevenly. Mild knocking may only increase noise without obvious engine damage, but severe knocking indicates serious engine conditions. The vibrations not only affect driving stability but also cause abnormal wear on pistons and cylinders, potentially leading to cylinder scoring in severe cases.