Can the Jetta VS7 use 92-octane gasoline for a long time?

[StKaleb]

According to the official vehicle manual recommendation, the Jetta VS7 should use 95-octane gasoline. In addition to checking the suitable gasoline grade in the vehicle manual, you can also find it on the fuel tank cap, which will be clearly marked. Generally, 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 some new technologies, the gasoline grade cannot be solely determined by the compression ratio. A high compression ratio can also be adjusted to use lower-grade gasoline because, apart from 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 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 Jetta VS7 occasionally uses the wrong gasoline grade, 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-grade gasoline, using higher-grade gasoline will not cause damage, but the increase in octane number will alter 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, resulting in poorer performance in actual driving experience. For vehicles recommended to use higher-grade gasoline, using lower-grade gasoline can cause engine knocking. Due to the significantly lower octane number, the gasoline's ignition point decreases, causing premature ignition during the compression stroke. If detonation 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 imperceptible, it only increases noise without obvious damage to the engine. However, noticeable knocking indicates severe engine conditions, where vibrations not only affect driving stability but also cause abnormal wear on pistons and cylinders, potentially leading to cylinder scoring in severe cases.

[LaSimon]

Regarding the long-term use of 92-octane gasoline in the Jetta VS7, I've driven this car for a while and think it's something to be cautious about. As a Volkswagen Group vehicle, the Jetta VS7's engine is quite sensitive to fuel, and manufacturers typically recommend 95-octane gasoline as more suitable. 92-octane fuel has a lower octane rating, and while short-term use might not show immediate issues, prolonged use can easily lead to engine knocking—noises during operation that feel like piston slapping, which can damage pistons and increase carbon buildup over time. I've tried using 92-octane a few times myself and noticed a significant increase in fuel consumption, with the car running less smoothly. During maintenance, the mechanic also warned that using the wrong fuel can shorten the engine's lifespan, and repairs can be extremely costly. So, I recommend checking the owner's manual. If you must use 92-octane, remember to regularly clean the fuel system and spark plugs to ensure high combustion efficiency. Additionally, fuel quality varies, so choosing reputable gas stations is safer—this habit is good for both fuel economy and maintenance.