What grade of gasoline should a Volkswagen CC use?

[LaNorah]

Volkswagen CC should use 95-octane gasoline, as recommended in the vehicle's official owner's manual. In addition to checking the appropriate gasoline grade in the owner's manual, you can also find it marked on the fuel tank cap. Typically, the gasoline grade can also be determined based on the engine's compression ratio. Vehicles with an engine 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. If the compression ratio is higher, 98-octane gasoline is recommended. However, with the use of new technologies, the compression ratio alone cannot determine the appropriate gasoline grade. A high compression ratio can also be tuned to use lower-octane gasoline, as factors such as ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Generally, the higher the gasoline grade, 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 a Volkswagen CC occasionally uses the wrong gasoline grade, simply switch back to the correct grade after the current tank is used up. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended to use lower-octane gasoline, using higher-octane gasoline will not cause damage, but the increase in octane number 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 to use higher-octane gasoline, using lower-octane gasoline can cause engine knocking. The significantly lower octane number lowers 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 unevenly. Mild knocking may only increase noise without significant engine damage, but severe knocking indicates serious engine conditions, affecting not only driving stability but also causing abnormal wear on the pistons and cylinders, potentially leading to cylinder scoring.