Should the 2007 Passat Lingyu use 92 or 95 octane fuel?

[Gimli]

The 2007 Passat should use 95 octane fuel, as recommended in the vehicle's official user manual. In addition to checking the appropriate fuel grade in the user manual, the 2007 Passat's fuel cap also indicates the recommended fuel type. 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 fuel, while those with a compression ratio between 10.0-11.5 should use 95 octane fuel. For higher compression ratios, 98 octane fuel is recommended. However, with the application of new technologies, the compression ratio alone cannot determine the fuel grade, as high compression ratio engines can also be tuned to use lower octane fuel. Other factors, such as ignition timing, turbocharging technology, and Atkinson cycle technology, also influence the fuel choice. Generally, higher octane fuel has a higher octane rating and better anti-knock properties. 92 octane fuel contains 92% isooctane and 8% n-heptane, while 95 octane fuel contains 95% isooctane and 5% n-heptane. If the 2007 Passat occasionally uses the wrong fuel grade, simply switch back to the correct grade after the current tank is used up. However, long-term use of the wrong fuel grade can have the following effects: For vehicles recommended to use lower octane fuel, using higher octane fuel will not cause damage, but the increased octane rating can 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 to use higher octane fuel, using lower octane fuel can cause engine knocking. The significantly lower octane rating reduces the fuel's ignition point, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires, resistance is created 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. The vibrations not only affect driving stability but also cause abnormal wear on the pistons and cylinders, potentially leading to cylinder scoring in severe cases.