Do I Need to Use Up All 92 Octane Gasoline Before Switching to 95 Octane?
3 Answers
It is recommended to completely use up the 92 octane gasoline before refueling with 95 octane, as this helps prolong the engine's service life. The reasons are as follows: 1. 92 octane and 95 octane gasoline have different stability levels. If mixed in large quantities, the gasoline's stability may be compromised. When driving with mixed gasoline, the engine may experience knocking or detonation, with noticeably increased vibrations, which can cause certain damage to the engine and lead to malfunctions. 2. When refueling, simply follow the instructions on the fuel tank cap. Of course, switching to a higher octane rating is not prohibited. However, based on practical experience, higher octane gasoline does not necessarily perform better nor provide additional engine protection. Many mid-to-high-end car engines have higher compression ratios, requiring more stable gasoline to reduce engine damage during combustion and extend engine life. Engines designed for 92 octane gasoline typically have relatively simpler structures and lower operational efficiency.
I've been driving for over a decade and have plenty of experience with changing gasoline grades. When switching from 92 to 95 octane, you don't necessarily have to wait until the tank is completely empty - mixing them is generally fine as the engine will automatically adjust ignition timing to accommodate different octane ratings. However, if you want to be precise, it's recommended to refill with 95 when about a quarter tank remains, as this minimizes the mixing ratio and allows the new fuel's anti-knock properties to perform better. I specifically consulted a 4S店 technician when changing grades, and he said unless your engine has an exceptionally high compression ratio, you won't feel any difference driving with half a tank of 92 mixed with half 95. The key is to avoid frequent grade switching - occasional mixing is harmless, and consistently using 95 can actually help clean carbon deposits in the long run.
Last time I took my car for maintenance, the mechanic mentioned this topic. He said that both 92 and 95 are essentially gasoline with similar additive formulas, so there's no need to deliberately empty the tank. He suggested that the most convenient way is to add 95 when the fuel light comes on, because the remaining fuel at the bottom of the tank might contain impurities, and mixing can actually dilute the deposits. Personally, when switching fuel types, I prefer to add 95 when the remaining range is about 100 kilometers. This avoids overheating the fuel pump while allowing the new octane rating to take effect as soon as possible. The only thing to note is that for turbocharged cars, mixing fuels might temporarily affect acceleration smoothness, but the onboard computer will adapt after running through half a tank.
