Is 92 or 95 Octane Gasoline Better?

[Ivan]

95 octane gasoline is better than 92 octane gasoline. Generally speaking, the higher the octane rating of gasoline, the higher the octane number 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. In addition to checking the appropriate gasoline grade in the car manual, you can also check it on the fuel tank cap, which will also be marked. Usually, you can also decide the gasoline grade based on the engine's compression ratio. Cars with an engine compression ratio between 8.6-9.9 should use 92 octane gasoline, while cars with an engine compression ratio between 10.0-11.5 should use 95 octane gasoline. If the compression ratio is higher, 98 octane gasoline should be used. However, with the use of some new technologies, the gasoline grade cannot be determined solely based on the compression ratio. A high compression ratio can also be adjusted to use lower octane gasoline. This is because, in addition to the compression ratio, other factors such as ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Occasionally using the wrong gasoline grade only requires switching back to the correct grade after use. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended for low octane gasoline, using higher octane gasoline will not cause damage, but the increase in octane number will change the fuel's ignition point, leading to delayed combustion in the engine. This means both the engine's power output and thermal efficiency will decrease, resulting in poorer performance. For vehicles recommended for high octane gasoline, using lower octane gasoline can cause engine knocking. Because the octane number 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 ignites during the compression stroke, resistance will occur during the upward stroke. This resistance will make the engine run very unstably. If it is only mild knocking, the noise will increase, but the damage to the engine is not significant. If there is obvious knocking, it indicates the engine's condition is very severe. The vibration not only affects driving stability but also causes abnormal wear on the piston and cylinder, and in severe cases, cylinder scoring.