The Mustang should use 92-octane gasoline, as this fuel grade is recommended in the vehicle's official owner's manual. In addition to checking the suitable gasoline grade in the owner's manual, you can also find it labeled on the fuel tank cap. Generally, the appropriate 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. If the compression ratio is even higher, 98-octane gasoline is recommended. However, with the application of new technologies, the gasoline grade should not be determined solely based on the compression ratio. High-compression engines can also 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 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 Mustang occasionally uses the wrong gasoline grade, simply switch back to the correct grade after the tank is empty. However, prolonged use of the wrong gasoline grade can have the following effects: For vehicles designed for low-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 high-octane gasoline, using a lower-octane grade can cause engine knocking. Because the octane number is too low, the fuel's ignition point decreases, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires, resistance is created during the upward stroke. This resistance makes the engine run very unstably. Mild knocking may only increase noise without significant engine damage, but severe knocking indicates serious engine issues. The vibrations not only affect driving stability but can also cause abnormal wear on pistons and cylinders, and in extreme cases, lead to cylinder scoring.
