Does Mixing 95 and 98 Octane Gasoline Have Any Impact?
2 Answers
92 octane gasoline and 95 octane gasoline should not be mixed because they have different iso-octane 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, it may cause abnormal combustion, 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, it may even cause engine damage. Conversely, if 95 octane gasoline is added to a car that requires 92 octane gasoline, although it won't damage the engine, it is more expensive and thus wasteful. Differences between 92, 95, and 98 octane gasoline: Standard gasoline is composed of iso-octane and n-heptane. Iso-octane has good anti-knock properties and is assigned an octane rating of 100, while n-heptane has poor anti-knock properties and is prone to knocking in gasoline engines, so it is assigned an octane rating of 0. If the gasoline is labeled as 92 octane, it means that this gasoline has the same anti-knock properties as a standard gasoline composed of 92% iso-octane and 8% n-heptane. The same principle applies to 95 and 98 octane gasoline. How to handle adding the wrong gasoline: If a higher octane gasoline than required is added (e.g., adding 95 octane when 92 octane is specified), simply use up the gasoline and then refill with 92 octane. If a lower octane gasoline than required is added (e.g., adding 92 octane when 95 octane is specified), you can add a high anti-knock fuel additive. Alternatively, you can drain the fuel tank and refill it with 95 octane gasoline. To determine the correct gasoline grade for your car, refer to the vehicle's user manual or check the fuel grade indicated on the fuel tank cap.
Mixing 95 and 98 octane gasoline has minimal impact. I've been driving for over a decade and often refuel with different grades during long trips. The key lies in the octane rating difference—95 has slightly lower anti-knock properties while 98 is higher. When mixed, the average settles around 96. Modern car electronic systems automatically adjust ignition timing to adapt. Unless your engine has an exceptionally high compression ratio or is modified (like my family car occasionally mixing fuels without issues), it's generally fine. However, avoid frequent mixing as long-term use may cause slight carbon buildup or increased fuel consumption. Remember, always follow the owner's manual recommendation for optimal fuel grade—don't cut corners by mixing.
