What Octane Gasoline Should an Audi A4 Use?

[MackenzieDella]

Audi A4 should use 95-octane gasoline. This octane rating is recommended in the vehicle's official owner's manual. In addition to checking the owner's manual for the appropriate gasoline octane, you can also find this information on the fuel filler cap, which will indicate the recommended octane. Typically, the required octane can also be determined by 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 higher, 98-octane gasoline is recommended. However, with the use of new technologies, the compression ratio alone cannot determine the required octane, 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 you occasionally use the wrong octane gasoline in an Audi A4, simply switch back to the correct octane after the tank is empty. However, long-term use of the wrong octane can have the following effects: Using a higher octane gasoline in a vehicle designed for lower octane will not cause damage, but the increased octane 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. Using a lower octane gasoline in a vehicle designed for higher octane can cause engine knocking. The significantly lower octane 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 unstably. 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 severe engine damage.