What Octane Gasoline Should an Alpha Use?

[LaMadelyn]

Alpha should use 92 octane gasoline, as this is the recommended fuel grade specified in the vehicle's official owner's manual. In addition to checking the appropriate gasoline grade in the owner's manual, Alpha owners can also find this information on the fuel filler cap, which is typically labeled. The choice of 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. For higher compression ratios, 98 octane gasoline is recommended. However, with the advent of new technologies, the compression ratio alone cannot determine the appropriate gasoline grade, as high-compression engines can be tuned to use lower-octane fuel. Other factors, such as ignition timing, turbocharging technology, and Atkinson cycle technology, also play a role. Generally, higher-octane gasoline has a higher octane rating and better anti-knock properties. For example, 92 octane gasoline contains 92% isooctane and 8% n-heptane, while 95 octane gasoline contains 95% isooctane and 5% n-heptane. If an Alpha is occasionally filled with the wrong gasoline grade, simply switching back to the correct grade after use is sufficient. However, prolonged use of the wrong gasoline grade can have the following effects: Using a higher-octane gasoline in a vehicle designed for lower-octane fuel will not cause damage, but the increased octane rating can 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. Using a lower-octane gasoline in a vehicle designed for higher-octane fuel can cause engine knocking. The significantly lower octane rating lowers the fuel'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 significant engine damage, but severe knocking indicates serious engine issues, affecting not only driving stability but also causing abnormal wear on pistons and cylinders, potentially leading to cylinder scoring.