Should the Older Mazda 6 Use 92 or 95 Octane Gasoline?

[EmilyFitz]

The older Mazda 6 can use 92 octane gasoline. This gasoline grade is recommended in the vehicle's official user manual. In addition to checking the appropriate gasoline grade in the user manual, the older Mazda 6 also has this information indicated on the fuel tank cap. 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 ratio between 10.0-11.5 should use 95 octane gasoline. If the compression ratio is even higher, 98 octane gasoline is recommended. However, with the application of new technologies, the compression ratio alone cannot determine the required gasoline grade, as high compression ratio 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 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 older Mazda 6 occasionally uses the wrong gasoline grade, simply switch back to the correct grade after the current tank is used up. However, prolonged use of the wrong gasoline grade can have the following effects: For vehicles designed for lower octane gasoline, using a higher octane grade will not cause damage, but the increased octane number 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 designed for higher octane gasoline, using a lower octane grade can cause engine knocking. The significantly lower octane number reduces the gasoline's ignition point, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires, resistance is generated during the upward stroke. This resistance makes the engine run very unevenly. Mild knocking may only increase noise without noticeable engine damage, but severe knocking indicates serious engine conditions. The vibrations not only affect driving stability but can also cause abnormal wear on pistons and cylinders, potentially leading to cylinder scoring in severe cases.