Should the Old Tiguan Use 95 or 92 Octane Gasoline?
2 Answers
The old Tiguan should use 95 octane gasoline, as this is the fuel grade officially recommended in the vehicle's user manual. In addition to checking the appropriate gasoline grade in the user manual, the old Tiguan also has this information indicated on the fuel tank cap. The fuel grade can usually 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 even higher, 98 octane gasoline is recommended. However, with the application of new technologies, the compression ratio alone cannot determine the required gasoline grade, as high-compression engines can also be tuned to use lower-octane fuel. 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 old Tiguan occasionally uses the wrong gasoline grade, simply switch back to the correct grade after the tank is empty. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles designed for lower-octane fuel, using higher-octane gasoline 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 designed for higher-octane fuel, using lower-octane gasoline can cause engine knocking. Due to the significantly lower octane number, the fuel may ignite prematurely during the compression stroke, creating resistance before the spark plug fires. This resistance can make the engine run very unstably. Mild knocking may only increase noise without obvious engine damage, but severe knocking indicates serious engine issues, affecting driving stability and causing abnormal wear on pistons and cylinders, potentially leading to cylinder scoring.
I've been driving an old Tiguan for five years, so this topic is very familiar to me. The engine has a relatively high compression ratio, and it's designed to run on 95-octane gasoline, which makes it perform smoother. While 92-octane is cheaper and occasionally using it is fine—like when only 92 is available at remote gas stations for emergency purposes—long-term use can cause issues. Low-octane fuel is more prone to causing knocking, increasing engine vibrations, accelerating carbon buildup over time, and even leading to higher fuel consumption and reduced power. A mechanic once mentioned that knocking could damage spark plugs and cylinders, and repairs wouldn't be cheap. Personally, I recommend prioritizing 95-octane fuel. Check the owner’s manual—it likely recommends 95 or 97 octane. This investment is worth it for better car condition, peace of mind, and hassle-free driving. On highways or during hot summer days, 95-octane provides better anti-knock performance and overall reliability. Make it a habit to fuel up at reputable gas stations and clean carbon deposits regularly to extend your car’s lifespan.
