Is There Any Harm in Using 98 Octane Gasoline in a Car Designed for 92 Octane?

[LeEthan]

Using 98 octane gasoline in a car designed for 92 octane does not harm the vehicle. Generally, the type of gasoline to be used is determined by the engine's compression ratio. The higher the compression ratio, the higher the anti-knock quality of the gasoline required; otherwise, engine knocking may occur. The minimum gasoline standard is usually indicated on the fuel tank cap, and it is advisable to follow these recommendations. Additional Information: If 92 octane gasoline is used in a car that requires 98 octane, mixing them for a short period may not cause significant issues. However, prolonged use can lead to engine knocking, especially noticeable during idling. Continuous mixed usage over time may also result in increased engine carbon deposits and higher fuel consumption.

[DiAlina]

I usually drive an old car that takes 92-octane gasoline. Once, the gas station only had 98-octane fuel, so I tried filling up with it. There were no noticeable abnormalities while driving, and the engine didn't throw any fault codes. However, the mechanic mentioned that higher-octane fuel has better anti-knock properties but burns slower, which might reduce combustion efficiency. On long trips, the fuel consumption actually increased by about 0.5 liters. The gas station attendant put it more bluntly, saying it's like putting racing fuel in a tricycle—the extra money spent could buy two tanks of 92-octane. In reality, the manufacturer's requirement for 92-octane is matched to the compression ratio; higher octane isn't always better. It's fine to use it once in an emergency, but long-term use could lead to carbon buildup.

[Stacey]

At the last class reunion, we talked about this. I've been running an auto repair shop for fifteen years. Using 98 octane fuel in a 92 octane engine won't damage the hardware, but the ECU needs time to adjust the ignition timing, which may cause power lag during the process. Some customers reported increased water dripping from the exhaust pipe during cold starts after switching to higher octane fuel, indicating the combustion temperature isn't at its optimal state. The most practical issue is the cost - the 98 octane at my shop costs 1.2 yuan more per liter than 92 octane. Driving 20,000 kilometers a year would mean spending over 2,000 yuan extra. Rather than fussing over octane ratings, it's more practical to regularly use fuel system cleaners to maintain the fuel lines.

[StCarter]

As an automotive engineering major, from a technical standpoint, using 98-octane fuel in a car designed for 92 isn't wrong. Higher-octane fuel has greater knock resistance, theoretically reducing engine knock. However, modern vehicle ECUs automatically adjust ignition timing based on knock sensor feedback – using 98-octane may actually cause the ECU to reduce performance output. Test data shows 92-octane engines using 98-octane fuel exhibit 0.3-second slower 0-100km/h acceleration and 5% higher hydrocarbon emissions. Unless your vehicle frequently carries heavy loads uphill or has a modified ECU, there's no real need. Remember, the recommended octane rating on your fuel cap is the optimal solution.