Should the Roewe RX5 use 92 or 95 octane gasoline?

[DelLilliana]

According to the official vehicle manual recommendation, the Roewe RX5 should use 92 octane gasoline. In addition to checking the appropriate gasoline grade in the vehicle manual, the Roewe RX5 can also refer to the label on the fuel tank cap. Typically, the required gasoline 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, 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 required gasoline grade, as high-compression engines can also 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 octane rating, 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 Roewe RX5 occasionally uses the wrong gasoline grade, simply refuel with the correct grade afterward. However, prolonged use of the wrong gasoline grade can have the following effects: For vehicles designed for lower octane gasoline, using higher octane fuel will not cause damage, but the increased octane number 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 designed for higher octane gasoline, using lower octane fuel can cause engine knocking. Due to the significantly lower octane number, the fuel may ignite prematurely during the compression stroke, creating resistance before the spark plug fires. This resistance leads to unstable engine operation. Mild knocking may only increase noise without significant engine damage, but severe knocking indicates serious engine issues, affecting driving stability and causing abnormal wear on pistons and cylinders, potentially leading to cylinder scoring.