According to the official car manual recommendation, the Golf should use 95 gasoline. Occasionally using the wrong gasoline grade only requires switching back to the correct grade after consumption. However, long-term use of the wrong gasoline grade will have the following effects: For vehicles recommended for lower grades, using higher-grade gasoline will not cause damage, but the increase in octane value will change the fuel's ignition point, leading to delayed combustion in the engine. This means both the engine's power output and thermal efficiency will decrease, with the actual feedback being reduced performance. For vehicles recommended for higher grades, using lower-grade gasoline will cause engine knocking. Because the octane value is too low, the reduced ignition point of the gasoline will cause it to ignite prematurely during the compression stroke. If combustion occurs before the spark plug ignites during the compression stroke, resistance will appear during the upward stroke. This resistance will make the engine run very unstably. If it's mild knocking, it only increases noise without significant damage to the engine. 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. In addition to checking the suitable gasoline grade in the car manual, Golf owners can also find it on the fuel tank cap, which will be clearly marked. Typically, the gasoline grade can also be determined based on the engine's compression ratio. Cars with a compression ratio between 8.6-9.9 should use 92 gasoline, while those between 10.0-11.5 should use 95 gasoline. However, with the use of new technologies, the compression ratio alone cannot determine the gasoline grade. High compression ratio engines can be tuned to use lower-grade gasoline because, besides the compression ratio, other 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 value and the better the anti-knock performance. 92 gasoline contains 92% isooctane and 8% n-heptane, while 95 gasoline contains 95% isooctane and 5% n-heptane.
