What grade of gasoline should the Volkswagen Sharan use?
1 Answers
The Volkswagen Sharan should use 95-octane gasoline. This fuel grade is recommended in the vehicle's official owner's manual. In addition to checking the appropriate gasoline grade in the owner's manual, you can also find this information on the fuel filler cap, which will be clearly marked. Typically, the 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. If the compression ratio is higher, 98-octane gasoline is recommended. However, with the application of new technologies, the compression ratio alone cannot solely determine the appropriate gasoline grade. Engines with high compression ratios can also be tuned to use lower-octane gasoline. This is because, apart from the compression ratio, other factors such as ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Generally, 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 Sharan occasionally uses the wrong gasoline grade, simply switch back to the correct grade after the tank is empty. However, prolonged use of the wrong gasoline grade can have the following effects: For vehicles designed for lower-octane gasoline, using a higher-octane grade 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, with the practical effect being poorer performance. For vehicles designed for higher-octane gasoline, using a lower-octane grade can cause engine knocking. Because the octane number is significantly lower, the gasoline's ignition point decreases, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires, resistance will build up during the upward stroke. This resistance makes the engine run very unevenly. If the knocking is mild, it may only increase noise without obvious engine damage. However, noticeable knocking indicates severe engine conditions, affecting not only driving stability but also causing abnormal wear on pistons and cylinders. In extreme cases, it can even lead to cylinder scoring.
