Should the BMW X6 use 95 or 98 octane gasoline?

[McCamila]

According to the official vehicle manual recommendation, the BMW X6 should use 95 octane gasoline. In addition to checking the appropriate gasoline grade in the vehicle manual, the BMW X6 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. High compression ratio engines can still be tuned to use lower octane gasoline because 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 BMW X6 occasionally uses the wrong gasoline grade, simply switching back to the correct grade after consumption is sufficient. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended to use lower octane gasoline, accidentally using higher octane gasoline will not cause damage, but the increase in octane value may alter the fuel's ignition point, leading to delayed combustion in the engine. This results in reduced engine performance and thermal efficiency, manifesting as poorer power output. For vehicles recommended to use higher octane gasoline, using lower octane gasoline can cause engine knocking. Due to the significantly lower octane value, the fuel'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 unstable. Mild knocking may only increase noise without significant engine damage, but 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.

[StLena]

I've been driving this BMW X6 for over five years and have always insisted on using 95-octane gasoline. In fact, the inside of the fuel tank cap clearly states 'Minimum 95-octane' – the manufacturer calibrated the engine with 95's anti-knock properties in mind. While 98-octane is certainly better with stronger anti-knock performance suitable for aggressive driving, 95 is perfectly adequate for daily commuting. During a recent maintenance visit to the dealership, the technician confirmed that long-term use of 95-octane won't harm the engine, as long as you refuel at reputable gas stations. Important reminder about fuel mixing: occasionally using 98 in emergencies is fine, but avoid frequent switching between grades, as the ECU constantly adjusting ignition timing could actually be detrimental to the engine.