Should the Volkswagen Santana use 92 or 95 octane gasoline?
2 Answers
According to the official car manual recommendation, the Volkswagen Santana should use 92 octane gasoline. In addition to checking the suitable gasoline grade in the car manual, the Volkswagen Santana 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 compression ratio. Cars 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 nowadays, the gasoline grade cannot be solely determined by the compression ratio. A high compression ratio can also be adjusted to use lower-grade gasoline. This is because, apart from the compression ratio, there are other influencing factors such as ignition timing, turbocharging technology, and Atkinson cycle technology. 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 Volkswagen Santana occasionally uses the wrong gasoline grade, simply switch back to the correct gasoline grade after use. However, if the wrong gasoline grade is used for a long time, the following effects may occur: For vehicles recommended to use lower-grade gasoline, using higher-grade gasoline by mistake will not cause damage, but 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, and the actual feedback experience is reduced power. For vehicles recommended to use higher-grade gasoline, using lower-grade gasoline will cause engine knocking. Because the octane number is too low, the fuel's ignition point decreases and may ignite prematurely during the compression stroke. If combustion occurs before the spark plug ignites during the compression stroke, resistance will appear during the upward stroke. This resistance will make the engine run very unstably. If it is only slight knocking, the noise will increase, but the damage to the engine is not obvious. If there is obvious knocking, it indicates that the engine's condition is already very severe. The vibration not only affects driving stability but also causes abnormal wear of the piston and cylinder, and in severe cases, cylinder scoring may occur.
When driving my Volkswagen Santana, I tried both 92 and 95 octane fuel and found that 92 is perfectly adequate for daily use. The manual states that 92 is the minimum requirement, but I noticed significantly smoother performance when switching to 95 during frequent highway driving. Higher-octane gasoline like 95 reduces engine knocking and protects the engine, especially during summer or uphill driving. Although 92 is more economical, 95 may offer slightly better fuel efficiency, making the long-term cost roughly the same. I recommend choosing based on driving conditions: 92 is fine for city commuting, but opt for 95 on long trips or spirited driving to ensure safety. My car has run for several years without major issues—following the manual is the most reliable approach.