What happens if you use 92 octane gasoline in a Volkswagen CC?

[JuliannaDella]

According to the official vehicle manual recommendation, the Volkswagen CC should use 95 octane gasoline. In addition to checking the suitable gasoline grade in the vehicle manual, you can also find it marked on the fuel tank cap of the Volkswagen CC. 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. However, with the application of new technologies, the compression ratio alone cannot determine the appropriate gasoline grade. High compression ratio engines can still be tuned to use lower octane gasoline 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 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 you occasionally use the wrong gasoline grade in a Volkswagen CC, simply switch back to the correct grade after consumption. 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 results in reduced engine power and thermal efficiency, with the practical effect being poorer performance. For vehicles recommended to use higher octane gasoline, using lower octane gasoline can cause engine knocking. Because the octane number is significantly lower, the reduced ignition point may cause premature ignition during the compression stroke. If combustion occurs before the spark plug ignites, resistance will arise during the upward stroke. This resistance makes the engine run very unstably. If the knocking is mild, it may only increase noise without obvious engine damage. However, noticeable knocking indicates severe engine conditions, affecting not only driving stability but also causing abnormal wear on pistons and cylinders, and in severe cases, cylinder scoring.