Is There Any Problem with Mixing 95 and 98 Octane Gasoline?

[Sadie]

Mixing 95 and 98 octane gasoline is problematic. If you occasionally fill up with the wrong gasoline grade, simply switch back to the correct one after using it up. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles designed for lower octane gasoline, using a higher octane grade will not cause damage, but the increase in octane rating can alter the fuel's ignition point, leading to delayed combustion in the engine. This results in reduced engine power and thermal efficiency, with the actual driving experience being poorer performance. For vehicles designed for higher octane gasoline, using a lower octane grade can cause engine knocking. Because the octane rating is too low, the gasoline's ignition point decreases, causing it to ignite prematurely during the compression stroke. If combustion occurs before the spark plug fires during the compression stroke, resistance will arise during the upward stroke. This resistance makes the engine run very unevenly. If the knocking is mild, it may only increase noise without significant engine damage. However, noticeable knocking indicates severe engine conditions, affecting not only driving stability but also causing abnormal wear on pistons and cylinders, and in severe cases, cylinder scoring. In addition to checking the recommended gasoline grade in the car's manual, you can also find it on the fuel tank cap. Typically, the gasoline grade can also be determined based on the engine's compression ratio. Cars with a compression ratio between 8.6-9.9 should use 92 octane gasoline, those between 10.0-11.5 should use 95 octane, and those with higher compression ratios should use 98 octane. However, with the use of new technologies, the compression ratio alone cannot determine the appropriate gasoline grade. High-compression engines can also be tuned to use lower octane gasoline due to other influencing factors, such as ignition timing, turbocharging technology, and Atkinson cycle technology. Generally, the higher the gasoline grade, the higher the octane rating and the better the anti-knock performance. 92 octane gasoline contains 92% isooctane and 8% n-heptane, while 95 octane gasoline contains 95% isooctane and 5% n-heptane.