According to the official vehicle user manual recommendation, Cadillac should use 92-octane gasoline. In addition to checking the appropriate gasoline grade in the vehicle user manual, Cadillac owners 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, 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 appropriate gasoline grade, as high-compression engines can also be tuned to use lower-octane gasoline. This is because 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 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 a Cadillac occasionally uses the wrong gasoline grade, simply switch back to the correct grade after the tank is empty. 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 increased octane value can 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 to use higher-octane gasoline, using a lower-octane grade can cause engine knocking. Since the octane value is significantly lower, the gasoline's ignition point decreases, causing premature ignition during the compression stroke. If combustion occurs before the spark plug ignites, resistance will arise during the upward stroke. This resistance makes the engine run very unstably. If the knocking is mild, it may only increase noise without significant engine damage. However, noticeable knocking indicates severe engine conditions, affecting not only driving stability but also causing abnormal wear on pistons and cylinders, potentially leading to cylinder scoring in severe cases.
