Is it okay to use 92 octane gasoline for the Tharu?
2 Answers
According to the official vehicle manual recommendation, the Tharu should use 95 octane gasoline. In addition to checking the appropriate gasoline grade in the vehicle 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. However, with the application of some new technologies, the gasoline grade cannot be solely determined by the compression ratio. A high compression ratio can still 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 Tharu occasionally uses the wrong gasoline grade, simply switch back to the correct grade after consumption. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended for lower octane gasoline, using higher octane gasoline will not cause damage, but the increase in octane number will alter the fuel's ignition point, leading to delayed combustion in the engine. This means both the engine's power output and thermal efficiency will decrease, resulting in poorer performance. For vehicles recommended for higher octane gasoline, using lower octane gasoline can cause engine knocking. Because the octane number is too low, the gasoline's ignition point decreases, leading to premature ignition during the compression stroke. If detonation occurs before the spark plug ignites, resistance will appear during the upward stroke. This resistance will make the engine run very unstably. If the knocking is imperceptible, it will only increase noise without significant damage to the engine. However, if noticeable knocking occurs, it indicates severe engine conditions, affecting not only driving stability but also causing abnormal wear on pistons and cylinders, and in severe cases, cylinder scoring.
The Volkswagen Tharu's engine is designed to recommend using 95-octane gasoline due to its high compression ratio. Using 92-octane fuel may lead to insufficient octane levels, which can cause knocking—premature ignition of fuel in the cylinder, potentially damaging pistons and valves. Modern engines are equipped with ECU computer control systems that adjust ignition timing to adapt automatically, preventing immediate major issues. However, prolonged use can result in decreased performance, increased fuel consumption, and more carbon buildup, ultimately proving cost-ineffective. Using 92-octane fuel occasionally in emergencies, such as when no other gas stations are available on a highway, is acceptable, but it's advisable to switch back to 95-octane as soon as possible to maintain engine health. Always check the owner's manual for confirmation—don't risk long-term damage to save money, as repairs can be far more expensive in the long run.
