Is it mandatory to use 95 octane gasoline for the Volkswagen Tiguan L?

[Angelo]

The Volkswagen Tiguan L must use 95 octane gasoline, as this fuel grade is officially recommended in the vehicle's user manual. In addition to checking the appropriate gasoline grade in the user manual, the recommended octane rating for the Volkswagen Tiguan L can also be found on the fuel tank cap, which will be clearly marked. Typically, the fuel 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. For higher compression ratios, 98 octane gasoline is recommended. However, with the application of new technologies, the compression ratio alone cannot determine the required gasoline grade, as high-compression engines can also be tuned to use lower-octane fuel. This is because factors other than compression ratio, 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 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 Volkswagen Tiguan L occasionally uses the wrong gasoline grade, simply switching back to the correct grade after consumption is sufficient. However, prolonged use of the wrong gasoline grade can have the following effects: For vehicles recommended to use lower-octane gasoline, using a higher octane fuel 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 a lower octane fuel can cause engine knocking. Due to the significantly lower octane number, the gasoline's ignition point decreases, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires, resistance will develop during the upward stroke. This resistance makes the engine run very unstably. 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, potentially leading to cylinder scoring in severe cases.