Should Mazda6 Use 92 or 95 Octane Gasoline?

[LaDominic]

Mazda6 can use 92 octane gasoline. This fuel grade is recommended in the vehicle's official user manual. In addition to checking the appropriate gasoline grade in the user manual, the recommended fuel grade is also 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 application of new technologies, the compression ratio alone cannot determine the appropriate fuel grade. High compression ratio engines can also be tuned to use lower octane gasoline due to other influencing factors such as ignition timing, turbocharging technology, and Atkinson cycle technology. Generally, the higher the gasoline grade, 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 Mazda6 occasionally uses the wrong gasoline grade, simply switch back to the correct grade after consumption. However, prolonged use of the wrong gasoline grade can have the following effects: For vehicles designed for lower octane gasoline, using higher octane gasoline 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 designed for higher octane gasoline, using lower octane gasoline can cause engine knocking. The significantly lower octane number reduces the fuel's ignition point, causing premature ignition during the compression stroke. If combustion occurs before the spark plug ignites, resistance is created during the upward stroke. This resistance leads to unstable engine operation. Mild knocking may only increase noise without significant engine damage, but severe knocking indicates serious engine conditions, affecting driving stability and causing abnormal wear on pistons and cylinders, potentially leading to cylinder scoring in extreme cases.