Does Using 92 Octane Gasoline Affect the Passat?
2 Answers
According to the official vehicle manual recommendation, the Passat should use 95 octane gasoline. In addition to checking the suitable gasoline grade in the vehicle manual, the Passat's fuel tank cap also indicates the recommended octane rating. Typically, the engine's compression ratio can also determine the appropriate gasoline grade. Vehicles with a 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 gasoline grade, as high compression ratios can be adjusted to use lower octane gasoline. Other factors, such as ignition timing, turbocharging technology, and Atkinson cycle technology, also play a role. Generally, the higher the gasoline octane rating, 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, simply switch back to the correct octane rating 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 a higher octane rating will not cause damage, but the increased 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, manifesting as poorer performance. For vehicles recommended to use higher octane gasoline, using a lower octane rating can cause engine knocking. The significantly lower octane number reduces the gasoline's ignition point, causing 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 imperceptible, it only increases noise without significant engine damage. However, noticeable knocking indicates severe engine conditions, affecting not only driving stability but also causing abnormal wear on pistons and cylinders, potentially leading to cylinder scoring in severe cases.
I've driven a Passat for many years. When I first bought the car, the 4S shop staff told me to use 95-octane gasoline and avoid 92-octane. Once when I was on a business trip, only 92-octane was available at the gas station, so I tried filling up with it. The engine started buzzing, acceleration felt weak, and there was severe shaking when going uphill. My friend, a car mechanic, explained that the Passat's engine has a high compression ratio, and 92-octane fuel has lower octane rating, which can easily cause knocking—that abnormal combustion sound. Over time, it can damage the ignition system and pistons, and repairs could cost thousands. Since then, I've stuck to 95-octane to avoid these troubles. For daily use, it's safest and easiest to follow the manual. Using 92-octane occasionally isn't a big deal, but don't make it a habit—otherwise, the car's lifespan will shorten, and repair costs will far exceed any savings on fuel.
