Can 98 and 95 gasoline be mixed?
2 Answers
95 gasoline and 98 gasoline can occasionally be mixed, but it is not recommended to mix them for a long time. The following is a specific introduction about gasoline: Long-term mixing of gasoline can cause engine knock. Gasoline is a mixture. The gasoline grade usually referred to is the anti-knock index (i.e., octane number) of gasoline. Strictly speaking, 95 gasoline and 98 gasoline cannot be mixed. However, their chemical compositions and other aspects are relatively similar, with strong anti-knock properties. To ensure vehicle safety, they should still be used separately. Some regions still have low-grade 90 gasoline. Mixing it with high-grade gasoline can cause knocking, insufficient power, and other phenomena. It will also affect the service life of spark plugs and bring more exhaust pollution. The density of 98 gasoline is generally above 0.74. 98 gasoline is gasoline whose octane number is equal to a mixture of 98% isooctane and 2% n-heptane. The advantages of 98 gasoline are "two highs and two lows," namely higher anti-knock performance and power performance, and lower harmful substances and exhaust pollution in the gasoline. 95 gasoline has strong anti-knock properties and will not be compressed and ignited under high pressure, ensuring the engine is at the optimal ignition timing, and the power output is not affected. The gasoline grade also represents the anti-knock performance of the fuel. The higher the grade, the better the anti-knock performance. Anti-knock performance refers to the ability of gasoline to resist knocking when burning in the engine. It is the primary indicator of gasoline combustion performance. Knocking is caused by abnormal combustion of gasoline in the engine. The octane number is precisely the target of gasoline's anti-knock performance. The higher the octane number, the stronger the anti-knock performance. The higher the compression ratio, the higher the pressure in the combustion chamber. If gasoline with low anti-knock performance is used, knocking is more likely to occur.
I remember once driving to a remote area where the gas station only had 95 octane fuel, while my car usually takes 98. I ended up mixing a full tank. It turned out okay—the car didn’t stall—but I noticed the acceleration felt slightly sluggish, and the engine sound was rougher than usual. Mixing gasoline averages the high octane of 98 with the mid-octane of 95, and the car’s ECU tries to adjust the ignition timing to prevent knocking, but this might not be optimal. Over time, it could lead to more carbon buildup or sensor issues. Later, I checked the manual, which recommends using only the specified fuel grade. Mixing is fine in a pinch but shouldn’t be done long-term. Now, I always plan my gas stops in advance to avoid such hassles. After all, the engine is the heart of the car, and proper maintenance ensures it runs smoothly and reliably for the long haul.