Is it necessary to use 95-octane gasoline for the Volkswagen Touran?

[McKeira]

Volkswagen Touran must use 95-octane gasoline, as this fuel grade is recommended in the vehicle's official user manual. In addition to checking the appropriate gasoline grade in the user manual, the Volkswagen Touran's fuel cap also indicates the recommended octane rating. Generally, 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 fuel grade, as high-compression engines can also be tuned to use lower-octane gasoline. Other factors, such as ignition timing, turbocharging technology, and Atkinson cycle technology, also play a role. Generally, higher-octane gasoline has a higher octane rating and better anti-knock properties. 92-octane gasoline contains 92% isooctane and 8% n-heptane, while 95-octane gasoline contains 95% isooctane and 5% n-heptane. If the Volkswagen Touran 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: Using a higher-octane gasoline in a vehicle designed for lower-octane fuel will not cause damage, but the increased octane rating 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. Using lower-octane gasoline in a vehicle designed for higher-octane fuel can cause engine knocking. The significantly lower octane rating lowers the fuel's ignition point, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires, resistance is generated during the upward stroke. This resistance makes the engine run very unstably. Mild knocking may only increase noise without noticeable 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.