Can 95 gasoline be added after using 98 gasoline?

[OEli]

Can 95 gasoline be added after using 98 gasoline? It is necessary to use up the 98 gasoline before adding 95 gasoline. Gasoline is a volatile and flammable liquid hydrocarbon mixture obtained from the fractional distillation, cracking, or pyrolysis of petroleum, which can be used as fuel. It appears as a transparent liquid, mainly composed of aliphatic hydrocarbons, cycloalkanes, and a certain amount of aromatic hydrocarbons. Precautions for refueling: 1. Refuel in the morning or evening when the temperature is relatively low, as the same volume of gasoline can have a higher mass; 2. When driving in the city, it is not advisable to fill the tank completely, as it will increase the engine load; 3. Do not wait until the fuel is completely empty before refueling, as insufficient fuel will not pass through the fuel pump, reducing its lifespan; 4. Avoid refueling during thunderstorms, as the fuel nozzle may introduce stray currents into the car's fuel tank, increasing the movement of unstable gasoline molecules and posing potential fire and explosion hazards.

[SanSimon]

Seeing this question reminds me of often warning friends not to use the wrong fuel. If your car is designed for 98-octane gasoline, it's best not to switch to 95-octane, as the significant difference in octane rating can cause knocking—that knocking sound from the engine damages spark plugs, cylinders, and even shortens engine life. This is especially true for high-performance cars or turbocharged engines, which are more sensitive. When mixing fuels, incomplete combustion occurs, increasing fuel consumption and polluting the environment. The manual emphasizes adhering to the specified octane rating. Temporarily using a small amount of 95-octane in an emergency might not cause major issues, as modern cars have sensors that automatically adjust ignition timing to reduce knocking, but don't rely on this. As a car owner, safety comes first—always check the fuel type before refueling. Saving a little money isn't worth making a big mistake. Regularly checking engine condition can prevent problems. If you accidentally use the wrong fuel, drive gently and use it up as soon as possible.

[LeJuniper]

I've had a similar experience. Normally using 98 octane saves fuel, but I once tried 95 octane to save money. The result was noticeably slower acceleration, though the engine didn't make any strange noises, and short-term city commuting didn't cause any issues. Lower gasoline octane means weaker anti-knock performance, and mixing might cause slight knocking, but the car's knock sensor will adjust ignition to prevent damage. This doesn't mean it's viable long-term—the manual clearly states not to go below 98 octane, though it's acceptable in emergencies as long as you refill with higher octane afterward. From a cost perspective, 95 octane is cheaper, but engine repairs are more expensive in the long run. If you do mix fuels, maintain a steady speed and avoid idling for too long after running low. I recommend not experimenting too often—safety and savings come from being careful.

[JulianaRose]

From a technical perspective, engines are designed based on octane rating compatibility. Using 95-octane fuel in a car designed for 98-octane may cause significant ignition point differences, leading to knocking—the sensors detect abnormal combustion and compensate by delaying ignition. However, this only addresses short-term risks; mixed fuel usage can easily lead to carbon buildup and reduced power output. While the engine management system adapts, it cannot fully prevent piston damage. The safe practice is to adhere to the manual's recommended octane rating; in emergencies, you can use 95-octane fuel and drive cautiously. Avoid completely mixing fuels or long-term substitution. Pay attention to knocking sounds as they indicate potential issues.