Should Volkswagen Use 92 or 95 Octane Gasoline?

[MicahMarie]

Volkswagen vehicles require gasoline with an octane rating of 92 or higher, and 95 octane gasoline can also be used. This octane rating is recommended in the vehicle's official owner's manual. In addition to checking the owner's manual for the appropriate octane rating, Volkswagen owners can also find this information on the fuel filler cap. Typically, the octane rating 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 use of new technologies, the compression ratio alone cannot determine the required octane rating, as high-compression engines can also be tuned to use lower-octane gasoline. Other factors, such as ignition timing, turbocharging technology, and Atkinson cycle technology, also play a role. Generally, the higher the 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 a Volkswagen owner occasionally uses the wrong octane gasoline, simply switching back to the correct octane rating after the tank is empty is sufficient. However, prolonged use of the wrong octane rating can have the following effects: For vehicles designed for lower octane ratings, using higher octane gasoline will not cause damage, but the increased octane number 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. For vehicles designed for higher octane ratings, 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 fires, resistance is created during the upward stroke. This resistance makes the engine run very unevenly. Mild knocking may only increase noise without significant engine damage, but noticeable knocking indicates severe 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.