Is it necessary to use 95-octane gasoline for the Hongqi H5?

[LeEliza]

According to the official vehicle manual recommendation, the Hongqi H5 should use 95-octane gasoline, so it is highly advisable to do so. In addition to checking the appropriate gasoline grade in the vehicle manual, the Hongqi H5's fuel cap also displays the recommended octane rating. Typically, the choice of gasoline can also be determined by 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 ratio between 10.0-11.5 should opt for 95-octane gasoline. However, with the application of new technologies, the compression ratio alone is no longer the sole determinant of the required gasoline grade. High-compression engines can now be tuned to use lower-octane fuel due to other influencing factors such as ignition timing, turbocharging technology, and Atkinson cycle technology. Generally, higher-octane gasoline has a higher octane rating and better anti-knock properties. 92-octane gasoline contains 92% isooctane and 8% n-heptane, while 95-octane gasoline consists of 95% isooctane and 5% n-heptane. If the Hongqi H5 is occasionally filled with the wrong gasoline grade, simply switching back to the correct grade after use is sufficient. However, prolonged use of the wrong octane rating can have the following effects: For vehicles designed for lower-octane fuel, using higher-octane gasoline will not cause damage, but the increased octane rating alters the fuel's ignition point, leading to delayed combustion in the engine. This results in reduced engine power and thermal efficiency, manifesting as poorer performance. Using lower-octane gasoline in a vehicle designed for higher-octane fuel can cause engine knocking. The significantly lower octane rating lowers the fuel's ignition point, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires, resistance builds up during the upward stroke. This resistance makes the engine run very unevenly. Mild knocking may only increase noise without significant engine damage, but noticeable knocking indicates severe engine conditions. The vibrations not only affect driving stability but also cause abnormal wear on pistons and cylinders, potentially leading to cylinder scoring in severe cases.