Should the Mercedes-Benz S450 use 95 or 98 octane gasoline?

[ChloeLynn]

According to the official vehicle manual recommendation, the Mercedes-Benz S450 should use 95 octane gasoline. In addition to checking the suitable gasoline grade in the vehicle manual, the Mercedes-Benz S450 can also refer to the label on the fuel tank cap. Typically, the gasoline grade can also be determined based on the engine's compression ratio. Vehicles with an engine compression ratio between 8.6-9.9 should use 92 octane gasoline, while those with a compression ratio between 10.0-11.5 should use 95 octane gasoline. However, with the application of new technologies, the compression ratio alone cannot determine the appropriate gasoline grade. A high compression ratio can still be adjusted 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 octane number, the higher the octane value 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 Mercedes-Benz S450 occasionally uses the wrong gasoline grade, simply switch back to the correct grade after consumption. However, long-term use of the wrong gasoline grade may 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 value may alter 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 may cause engine knocking. Due to the significantly lower octane value, the reduced ignition point may cause premature ignition during the compression stroke. If combustion occurs before the spark plug ignites, resistance will arise during the upward stroke. This resistance makes the engine operation very unstable. If the knocking is imperceptible, it only increases noise without obvious engine damage. However, noticeable knocking indicates severe engine conditions, affecting not only driving stability but also causing abnormal wear on pistons and cylinders, potentially leading to cylinder scoring in severe cases.