Should the Roewe RX5 Plus use 92 or 95 octane gasoline?

[DeSara]

According to the official vehicle manual recommendation, the Roewe RX5 Plus should use 92 octane gasoline. In addition to checking the appropriate gasoline grade in the vehicle manual, the Roewe RX5 Plus can also find this information on the fuel tank cap, which will be clearly marked. 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, those between 10.0-11.5 should use 95 octane gasoline, and if the compression ratio is higher, 98 octane gasoline should be selected. However, with the application of some new technologies nowadays, the gasoline grade cannot be solely determined by the compression ratio. High compression ratio engines can also be tuned to use lower octane gasoline. This is because, apart from the compression ratio, other factors such as ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Generally speaking, 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 Roewe RX5 Plus occasionally uses the wrong gasoline grade, simply switch back to the correct grade after the current tank is used up. 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 means both the engine's power output and thermal efficiency will decrease, resulting in poorer performance as experienced by the driver. For vehicles recommended to use higher octane gasoline, using lower octane gasoline can cause engine knocking. This is because the significantly lower octane number reduces the fuel's ignition point, causing it to ignite prematurely during the compression stroke. If the fuel ignites before the spark plug fires during the compression stroke, resistance will occur during the upward stroke. This resistance makes the engine run very unstably. If the knocking is imperceptible, it only increases noise without obvious damage to the engine. However, noticeable knocking indicates severe engine conditions, where the vibrations not only affect driving stability but also cause abnormal wear on the pistons and cylinders, potentially leading to cylinder scoring in severe cases.