Can You Add 95 Octane Gasoline to a Tank with 92 Octane Gasoline?
2 Answers
You can add 95 octane gasoline to a tank with 92 octane gasoline, as different octane ratings of gasoline do not cause chemical reactions. Gasolines with different octane ratings have varying levels of octane numbers; the higher the octane rating, the higher the octane number, and the more stable the gasoline. Some vehicles require high-octane gasoline to prevent engine knocking. Knocking is an abnormal combustion phenomenon in the engine, which can affect the engine's power output and fuel economy. Severe knocking may even cause damage to the engine. Knocking occurs during the compression stroke when the intake and exhaust valves are closed, and the piston compresses the air-fuel mixture upwards.
As someone who frequently helps friends with car maintenance, I think mixing 92 and 95 octane fuel is quite common. Nowadays, car ECU computers are quite smart - when sensors detect changes in fuel grade, they automatically adjust ignition timing. That time when my relative's car had just been filled with 92 octane and then topped up with 95 at a halfway stop, it drove without even a hint of jerking. But be aware that older cars or turbocharged engines might trigger a warning light, since high-compression engines are more sensitive to knocking. Personally, I'd suggest that unless it's urgent, it's safer to wait until the 92 octane fuel level drops to one quarter before adding 95 octane - this way the mixing ratio is smaller and the engine transitions more smoothly. If you really can't find 92 octane during a long trip, temporarily mixing in 95 octane as an emergency measure is completely fine.
