Does using 92 octane gasoline affect the Passat?
2 Answers
According to the official vehicle manual recommendation, the Passat should use 95 octane gasoline, and 92 octane gasoline is not suitable. In addition to checking the appropriate gasoline grade in the vehicle manual, the Passat can also check it on the fuel tank cap, which will also be marked. Usually, the gasoline grade can also be determined according to the compression ratio of the engine. Cars with an engine compression ratio between 8.6-9.9 should choose 92 octane gasoline, while cars with an engine compression ratio between 10.0-11.5 should choose 95 octane gasoline. However, with the use of some new technologies nowadays, the gasoline grade cannot be determined solely based on the compression ratio. A high compression ratio can also be adjusted to use low-grade gasoline because, in addition to the compression ratio, other factors such as ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Generally speaking, 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 the Passat occasionally uses the wrong gasoline grade, it only needs to switch back to the correct gasoline grade after use. However, if the wrong gasoline grade is used for a long time, the following effects may occur: It is recommended that vehicles with low-grade gasoline mistakenly using high-grade gasoline will not be damaged, but the increase in octane number will change the ignition point of the fuel, causing the engine to experience delayed ignition. This means that the engine's working capacity and thermal efficiency will be reduced, and the actual feedback experience is that the power becomes worse. It is recommended that vehicles with high-grade gasoline using low-grade gasoline will cause engine knocking. Because the octane number is much lower, the ignition point of the gasoline will decrease and be ignited prematurely during the compression stroke. Once the gasoline ignites before the spark plug during the compression stroke, resistance will occur during the upward stroke. This resistance will cause the engine to run very unstable. If it is only slight knocking, the noise will increase, and the damage to the engine is not obvious. If there is obvious knocking, it means that the engine's working condition is already very serious. The vibration not only affects driving stability but also causes abnormal wear of the piston and cylinder, and in severe cases, it can even lead to cylinder scoring.
It's best not to use 92 octane fuel for the Passat. As a long-time Volkswagen owner, I can tell you that this car's engine has a high compression ratio. The manual clearly recommends 95 or 97 octane. Using 92 for extended periods can easily cause engine knocking. A friend of mine stubbornly used 92 for half a year, and the engine warning light kept coming on. In the end, it cost him over 3,000 yuan in repairs. Using it once or twice in an emergency is fine, but never use it long-term - it severely damages the car. Volkswagen's turbo engines are quite sensitive. Mechanics have told me that 92 octane fuel makes the knock sensor intervene frequently, which actually leads to higher fuel consumption. If you really want to save money, focus on driving habits - easing off the brakes is more reliable than downgrading fuel grade.
