The Mercedes-Benz GLC300 should use 95 octane gasoline, as this is the recommended fuel grade specified in the vehicle's official user manual. In addition to checking the appropriate gasoline grade in the user manual, you can also find it indicated on the fuel tank cap of the Mercedes-Benz GLC300. Generally, the fuel grade can also be determined based on the engine's compression ratio. Vehicles 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 higher compression ratios may require 98 octane. However, with the use of new technologies, the compression ratio alone cannot determine the required gasoline grade, as high compression ratios can now be tuned to use lower octane fuels. 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 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 Mercedes-Benz GLC300 occasionally uses the wrong gasoline grade, simply switch back to the correct grade after use. However, long-term use of the wrong grade can have the following effects: For vehicles designed for lower octane gasoline, using a higher octane grade will not cause damage, but the increased octane number can 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 designed for higher octane gasoline, using a lower octane grade can cause engine knocking. The significantly lower octane number lowers the fuel's ignition point, causing premature ignition during the compression stroke. If the fuel ignites before the spark plug fires, resistance occurs during the upward stroke. This resistance makes the engine run very unstably. Mild knocking may only increase noise without significant engine damage, but 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.
