Should the BMW 530 Use 95 or 98 Octane Gasoline?

[MacJourney]

According to the official vehicle manual recommendation, the BMW 530 should use 95 octane gasoline. In addition to checking the appropriate gasoline grade in the vehicle manual, the BMW 530 can also refer to the label on the fuel tank cap, which will indicate the recommended grade. Typically, the gasoline grade can also be determined based on the engine's compression ratio. Vehicles with a 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, as high compression ratios can be adjusted to use lower octane gasoline. Other 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 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 BMW 530 occasionally uses the wrong gasoline grade, simply switching back to the correct grade after use is sufficient. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended for low-octane gasoline, using a higher octane grade will not cause damage, but the increased octane number may alter 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. For vehicles recommended for high-octane gasoline, using a lower octane grade can cause engine knocking. Due to the significantly lower octane number, 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 imperceptible, it only increases noise without obvious 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.