Does switching from long-term use of 95-octane gasoline to 92-octane have any impact?
2 Answers
Switching from long-term use of 95-octane gasoline to 92-octane does have an impact. Occasionally using the wrong gasoline grade only requires switching back to the correct grade after consumption, but long-term use of the wrong gasoline grade can lead to the following effects: For vehicles recommended for low-octane gasoline, accidentally using high-octane gasoline will not cause damage. However, 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 a noticeable drop in performance. For vehicles recommended for high-octane gasoline, using low-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 fires, resistance will arise during the upward stroke. This resistance makes the engine run very unevenly. If the knocking is mild, it may only increase 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 addition to checking the appropriate gasoline grade in the vehicle's manual, you can also find it on the fuel tank cap. Generally, the gasoline grade can also be determined based on the engine's compression ratio. 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 suitable gasoline grade. High-compression engines can be tuned to use low-octane gasoline due to factors like ignition timing, turbocharging technology, and Atkinson cycle technology. 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.
I've been driving a family sedan for several years, initially always using 95-octane fuel, feeling the power was stable and comfortable. After fuel prices rose, I tried switching to 92-octane. For the first few days, there was no noticeable difference, but later during acceleration, the engine occasionally had slight vibrations. I looked it up and learned that lower octane fuel has poorer anti-knock properties, which might cause knocking noises. The ECU automatically adjusts ignition timing to adapt, avoiding major issues, but long-term use might lead to slightly more carbon deposits, affecting engine lifespan. Fortunately, my car's manual states it's compatible with 92-octane. Now I usually use 92 to save money, and periodically drive on highways to clean out carbon deposits. I recommend checking the manual's requirements before switching—if it specifies a minimum of 95-octane, don't switch to 92 to avoid unnecessary repair costs. From my experience, adaptability varies, but I don’t strongly recommend taking risks. During maintenance, the mechanic also said fuel octane impact varies by individual, with the key being observation of the car's condition.
