Should the Elantra use 92 or 95 octane gasoline?

[McBarrett]

The Elantra can use 92 octane gasoline. This fuel grade is officially recommended in the vehicle's user manual. In addition to checking the appropriate gasoline grade in the car's user manual, it can also be found on the fuel tank cap. Typically, the fuel grade can also be determined based on the engine's compression ratio. Cars with an engine compression ratio between 8.6-9.9 should use 92 octane gasoline, those between 10.0-11.5 should use 95 octane gasoline, and those with higher compression ratios should use 98 octane gasoline. However, with the use of new technologies, the compression ratio alone cannot determine the required gasoline grade, as high compression ratio engines can also be tuned to use lower octane gasoline. This is because factors other than compression ratio, such as ignition timing, turbocharging technology, and Atkinson cycle technology, also play a role. Generally, the higher the gasoline grade, 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. If the Elantra occasionally uses the wrong gasoline grade, simply switch back to the correct grade after finishing the tank. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended to use lower 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 reduces the engine's power output and thermal efficiency, resulting in poorer performance. For vehicles recommended to use higher octane gasoline, using lower octane gasoline can cause engine knocking. Due to the significantly lower octane number, 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 is created during the upward stroke. This resistance makes the engine run very unstable. If the knocking is mild, it only increases noise without significant damage to the engine. 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.