Is There Any Impact of Mixing 92 and 95 Octane Gasoline?
3 Answers
92 octane gasoline and 95 octane gasoline should not be mixed because they have different isooctane contents. 92 octane gasoline is suitable for engines with low compression ratios, while 95 octane gasoline is suitable for engines with high compression ratios. If 92 octane gasoline is added to a car that requires 95 octane gasoline, abnormal combustion may occur, leading to engine knocking. Knocking not only damages the combustion chamber but also directly affects the normal operation of the engine, and in severe cases, may cause engine damage. If 95 octane gasoline is added to a car that requires 92 octane gasoline, although it won't damage the engine, 95 octane gasoline is more expensive than 92 octane, resulting in unnecessary costs. Differences between 92, 95, and 98 octane gasoline: Standard gasoline is composed of isooctane and n-heptane. Isooctane has good anti-knock properties, with its octane rating set at 100, while n-heptane has poor anti-knock properties and is prone to knocking in gasoline engines, with its octane rating set at 0. If the gasoline is labeled as 92 octane, it means the gasoline has the same anti-knock properties as a standard gasoline composed of 92% isooctane and 8% n-heptane. The same principle applies to 95 and 98 octane gasoline. What to do if the wrong gasoline is added: If a higher octane gasoline than required is added, for example, adding 95 octane when the car requires 92 octane, simply use up the gasoline and then refill with 92 octane gasoline. If a lower octane gasoline than required is added, for example, adding 92 octane when the car requires 95 octane, you can add a high anti-knock fuel additive. Alternatively, you can drain the gasoline and refill with 95 octane gasoline. To determine the correct gasoline for your car, refer to the vehicle's user manual or check the fuel grade labeled on the fuel tank cap.
I've been driving for twenty years and have seen many friends accidentally mix 92 and 95 octane gasoline. That time I helped my neighbor watch his car, and when he went to refuel, he panicked and mixed half a tank of 92 with half a tank of 95. The car ran normally for a while without any major issues. However, doing this long-term is definitely not advisable because 92 octane has a lower octane rating and poorer anti-knock performance. Mixing too much can cause engine knocking, which means abnormal combustion, leading to reduced power or even damage to the spark plugs. Especially for high-end cars designed to use 95 octane, frequently mixing with 92 can easily trigger the check engine light. My advice is not to panic if you make an occasional mistake—just use a few tanks of the specified octane to adjust back. Develop the habit of checking the fuel grade carefully to avoid costly repairs later.
My car requires 95-octane fuel, and last time I used 92-octane, I felt the acceleration became slightly sluggish. Modern engines are equipped with intelligent sensors that can automatically adjust ignition timing to mitigate the issue, so mixing once won't kill the engine. However, doing it multiple times will strain the system, potentially increasing fuel consumption, and over time, it may damage the cylinder block and sensors. This is related to the engine's compression ratio design: 95-octane fuel is suitable for high-pressure engines to prevent knocking, while mixing lower-octane fuel means pushing it to the edge. It's best not to mix fuels randomly to save money—stick to the manual's recommendation to ensure smooth operation.
