Should the A4L use 92 or 95 octane gasoline?
2 Answers
According to the official vehicle manual recommendation, the A4L should use 95 octane gasoline. In addition to checking the appropriate gasoline grade in the vehicle manual, the A4L can also check it on the fuel tank cap, which will also be marked. Usually, the gasoline grade can also be determined based on the engine's compression ratio. Vehicles with an engine compression ratio between 8.6-9.9 should choose 92 octane gasoline, while those with a compression ratio between 10.0-11.5 should choose 95 octane gasoline. However, with the use of some new technologies, the gasoline grade cannot be determined solely by the compression ratio. A high compression ratio can also be tuned to use lower octane gasoline. This is because, in addition to the compression ratio, other factors such as ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Generally speaking, 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 the A4L occasionally uses the wrong gasoline grade, simply switch back to the correct grade after use. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended to use lower octane gasoline, using higher octane gasoline will not cause damage. However, the increase in octane number will change the fuel's ignition point, leading to delayed combustion in the engine. This means the engine's power output and thermal efficiency will decrease, resulting in poorer performance. For vehicles recommended to use higher octane gasoline, using lower octane gasoline can cause engine knocking. Because the octane number is too low, the gasoline's ignition point decreases, causing it to ignite prematurely during the compression stroke. If the fuel ignites before the spark plug fires during the compression stroke, resistance will occur during the upward stroke. This resistance will make the engine run very unstable. If the knocking is mild, it will only increase noise without significant damage to the engine. However, if the knocking is severe, it indicates that the engine's condition is very serious. The vibration not only affects driving stability but can also cause abnormal wear on the piston and cylinder, and in severe cases, even cylinder scuffing.
I've read the Audi A4L manual, which clearly states that the engine is turbocharged with a high compression ratio, requiring 95-octane gasoline. Using 92-octane fuel, which has a lower octane rating, can easily cause knocking issues—sounds like the engine 'clicking'—and lead to severe wear over time. Don't save that small amount of money; long-term use of 92-octane fuel not only reduces power but may also increase fuel consumption and exceed emissions standards, resulting in even scarier repair bills. I recommend always choosing 95-octane fuel to protect the car's heart. If you accidentally fill up with 92 once, it's fine, but quickly top it off with 95 to dilute the mixture and avoid accumulating problems. Safety comes first when driving—following the manual is always the right choice.
