Should the Buick GL6 Use 92 or 95 Octane Gasoline?

[StJesse]

According to the official vehicle manual recommendation, the Buick GL6 should use 92 octane gasoline. In addition to checking the appropriate gasoline grade in the vehicle manual, you can also find it on the fuel tank cap, which will also indicate the recommended octane. Generally, 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. However, with the application of new technologies, the compression ratio alone cannot determine the gasoline grade. High-compression engines can also be tuned to use lower-octane gasoline because, besides the compression ratio, other factors such as ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Generally, the higher the gasoline octane number, the higher the octane value 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 Buick GL6 occasionally uses the wrong gasoline grade, simply switch back to the correct octane after the tank is empty. However, prolonged use of the wrong gasoline grade can have the following effects: For vehicles recommended for low-octane gasoline, using a higher octane will not cause damage, but the increased octane value 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 recommended for high-octane gasoline, using a lower octane can cause engine knocking. The significantly lower octane value reduces 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 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 can also cause abnormal wear on the pistons and cylinders, potentially leading to cylinder scoring in severe cases.