Can a Car Designed for 95 Octane Use 98 Octane?

[AlessandraLee]

A car designed for 95 octane cannot use 98 octane. Occasionally using the wrong gasoline grade only requires switching back to the correct grade after use. However, prolonged use of the wrong gasoline grade can have the following effects: For vehicles recommended for lower octane, accidentally using higher octane gasoline will not cause damage, but the increase in octane rating changes the fuel's ignition point, leading to delayed combustion in the engine. This reduces the engine's power output and thermal efficiency, resulting in poorer performance. For vehicles recommended for higher octane, using lower octane gasoline can cause engine knocking. Because the octane rating is too low, the gasoline's ignition point decreases, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires, resistance is created during the upward stroke. This resistance makes the engine run very unstably. If the knocking is mild, it only increases noise without significant engine damage. However, severe knocking indicates serious engine conditions, affecting not only driving stability but also causing abnormal wear on pistons and cylinders, and in extreme cases, cylinder scoring. In addition to checking the appropriate gasoline grade in the car's manual, you can also find it on the fuel tank cap. Usually, the gasoline grade can also be determined by the engine's compression ratio. Cars with a compression ratio between 8.6-9.9 should use 92 octane, those between 10.0-11.5 should use 95 octane, and those with higher compression ratios should use 98 octane. However, with modern technologies, the compression ratio alone cannot determine the gasoline grade, as high compression ratios can be tuned to use lower octane gasoline. Other factors, such as ignition timing, turbocharging technology, and Atkinson cycle technology, also play a role. 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.