What grade of gasoline should a Volkswagen Tiguan use?
2 Answers
The Tiguan 1.8T can use 92-octane gasoline, while other models can use 95-octane gasoline. This gasoline grade is recommended in the vehicle's official user manual. In addition to checking the appropriate gasoline grade in the user manual, you can also find it on the fuel tank cap, which will be clearly marked. Generally, 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 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 even higher, 98-octane gasoline is recommended. However, with the use of new technologies, the compression ratio alone cannot determine the gasoline grade—engines with high compression ratios can also be tuned to use lower-octane gasoline. This is because, besides 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 Tiguan occasionally uses the wrong gasoline grade, simply switch back to the correct grade after refueling. However, prolonged use of the wrong gasoline grade may have the following effects: For vehicles recommended to use lower-octane gasoline, using a higher grade will not cause damage, but the increased octane number may 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. For vehicles recommended to use higher-octane gasoline, using a lower grade may cause engine knocking. Due to the significantly lower octane number, the gasoline's ignition point decreases, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires, resistance will develop during the upward stroke. This resistance makes the engine run very unstably. If the knocking is mild, it may only increase noise without obvious damage to the engine. However, if severe knocking occurs, it indicates serious engine conditions, affecting not only driving stability but also causing abnormal wear on the pistons and cylinders. In extreme cases, it may even lead to cylinder scoring.
I've been driving a Volkswagen Tiguan for ten years, and the turbocharged engine of this car is particularly delicate, requiring 95-octane gasoline. In the early years, I tried saving money by using 92-octane, but the engine would rattle as soon as I stepped on the accelerator, with noticeably weaker power and even higher fuel consumption. Later, I checked the manual, which clearly recommends 95-octane because the higher octane rating reduces knocking and protects the cylinders and pistons. Now, I never hesitate at the gas station and always choose 95-octane. Although it costs a few cents more per liter, the car runs smoothly and reliably, saving me the expense of major repairs. Especially during the high temperatures of summer, 95-octane fuel ensures stable performance and avoids the embarrassment of breaking down halfway.
