Should the 2020 Hongqi H5 use 92 or 95 octane gasoline?

[DeJosiah]

According to the official vehicle manual recommendation, the 2020 Hongqi H5 should use 95 octane gasoline. In addition to checking the appropriate gasoline grade in the vehicle manual, the 2020 Hongqi H5 can also refer to the fuel cap, which will indicate the recommended gasoline grade. 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. If the compression ratio is higher, 98 octane gasoline is recommended. However, with the application of some new technologies, the gasoline grade cannot be solely determined by the compression ratio. Engines with high compression ratios 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, 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 2020 Hongqi H5 occasionally uses the wrong gasoline grade, simply switch back to the correct grade after the current tank is used up. However, prolonged use of the wrong gasoline grade can have the following effects: For vehicles recommended to use lower octane gasoline, using a higher octane grade will not cause damage, but the increase in octane number may alter the fuel's ignition point, leading to delayed combustion in the engine. This can reduce the engine's power output and thermal efficiency, resulting in poorer performance. For vehicles recommended to use higher octane gasoline, using a lower octane grade can cause engine knocking. This is because the significantly lower octane number reduces the gasoline's ignition point, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires, resistance will develop during the upward stroke. This resistance can make the engine run very unstably. If the knocking is mild, it may only increase noise without obvious damage to the engine. However, if noticeable knocking occurs, it indicates severe engine conditions, affecting not only driving stability but also causing abnormal wear on the piston and cylinder, and in severe cases, cylinder scoring.