Must the Passat use 95-octane gasoline?

[LaAdaline]

According to the official vehicle manual recommendation, the Passat should use 95-octane gasoline. If the Passat occasionally uses the wrong gasoline grade, simply switch back to the correct grade after consumption. However, prolonged use of the wrong gasoline grade may have the following effects: For vehicles recommended for lower octane, using higher octane gasoline will not cause damage, but the increase in 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, with the actual feedback being poorer performance. For vehicles recommended for higher octane, using lower octane gasoline may cause engine knocking. Due to the significantly lower octane rating, the gasoline's ignition point decreases, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires, 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 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 addition to checking the recommended gasoline grade in the vehicle manual, the Passat's fuel filler cap also indicates the appropriate octane rating. Generally, 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 required gasoline grade. High compression ratio engines can still be tuned to use lower octane gasoline due to other influencing factors such as ignition timing, turbocharging technology, and Atkinson cycle technology. 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.