What grade of gasoline should a Mustang use?
2 Answers
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 marked on the fuel tank cap. Typically, 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, those between 10.0-11.5 should use 95-octane gasoline, and if the compression ratio is higher, 98-octane gasoline should be used. However, with the use of some new technologies, the fuel grade cannot be solely determined by the compression ratio. A high compression ratio can also be adjusted to use lower-grade gasoline because, besides the compression ratio, 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 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 a Mustang occasionally uses the wrong gasoline grade, simply switch back to the correct grade after using it up. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended to use lower-grade gasoline, using higher-grade gasoline will not cause damage, but the increase in octane number will change the fuel's ignition point, leading to delayed combustion in the engine. This means both the engine's power output and thermal efficiency will decrease, resulting in poorer performance. For vehicles recommended to use higher-grade gasoline, using lower-grade gasoline can cause engine knocking. Because the octane number is too low, the fuel's ignition point decreases and may ignite prematurely during the compression stroke. If combustion occurs before the spark plug fires during the compression stroke, resistance will arise during the upward stroke. This resistance can make the engine run very unstably. If the knocking is imperceptible, it only increases noise and does not significantly damage the engine. However, if the knocking is noticeable, it indicates severe engine conditions, affecting not only driving stability but also causing abnormal wear on the pistons and cylinders, and in severe cases, cylinder scoring.
I've been driving a Mustang 5.0 for three years, and fueling depends on the specific model. The older naturally aspirated engine runs perfectly fine on 92 octane - the manual clearly states regular unleaded gasoline is suitable. But if you frequently push high RPMs for power, like during mountain runs or track days, 95 octane makes the engine quieter with noticeably less knocking. Especially when climbing hills with AC on and full load in summer, higher octane fuel shows less power drop-off. Always choose Sinopec or PetroChina stations - I learned the hard way that 95 octane from small stations can be worse quality than 92 from major brands.
