The Nissan Qashqai should use 92 octane gasoline, as this is the fuel grade officially recommended in the vehicle's user manual. In addition to checking the appropriate gasoline grade in the user manual, you can also find it indicated on the fuel tank cap. Generally, the fuel 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. For higher compression ratios, 98 octane gasoline is recommended. However, with the use of new technologies, the compression ratio alone cannot determine the appropriate gasoline grade, as high compression ratios can now be tuned to use lower octane fuel. Other factors, such as ignition timing, turbocharging technology, and Atkinson cycle technology, also play a role. Generally, the higher the gasoline grade, the higher the octane rating 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 Qashqai occasionally uses the wrong gasoline grade, simply switch back to the correct grade after consumption. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended for lower octane fuel, using a higher octane grade will not cause damage, but the increased octane rating 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 for higher octane fuel, using a lower octane grade can cause engine knocking. The significantly lower octane rating lowers 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 unstably. 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, and in severe cases, cylinder scoring.
