What does 91 and 95 mean on the fuel tank cap of Audi A6L?
1 Answers
Audi A6L fuel tank cap showing 91 and 95 means this vehicle must use gasoline with octane ratings between 91-95. The differences between 92 and 95 octane gasoline are as follows: Different compositions: 92 octane gasoline contains approximately 92% isooctane and 8% n-heptane, while 95 octane gasoline contains about 95% isooctane and 5% n-heptane. Isooctane has better anti-knock properties, whereas n-heptane has poorer anti-knock performance. Therefore, higher octane numbers indicate higher anti-knock quality. Each engine is factory-rated with specific anti-knock requirements based on its performance characteristics, determining which octane gasoline should be used. Price difference: 95 octane gasoline is slightly more expensive per tank than 92 octane. Performance difference: Higher-octane 95 gasoline is suitable for engines with higher compression ratios. As these engines increase speed, ignition timing advances. When reaching a critical point, pre-ignition may occur where fuel-air mixture combusts before spark plug ignition - this phenomenon is called "knocking." Increasing gasoline's octane rating effectively improves anti-knock performance.