Should Cars Use 92 or 95 Octane Gasoline?
2 Answers
The octane rating of gasoline to be used in a car should be based on the recommendations in the vehicle's official user manual. In addition to checking the appropriate gasoline octane rating in the user manual, you can also find it on the fuel tank cap, which usually indicates the recommended rating. Typically, the octane rating can also be determined by the engine's compression ratio. Cars 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 use of new technologies, the octane rating can no longer be solely determined by the compression ratio. Engines with high compression ratios can also be tuned to use lower-octane gasoline. This is because factors other than the compression ratio, such as ignition timing, turbocharging technology, and Atkinson cycle technology, also play a role. Generally, the higher the octane rating, 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. Occasionally using the wrong octane rating only requires switching back to the correct one after the tank is empty. However, prolonged use of the wrong octane rating can have the following effects: For vehicles designed for lower octane ratings, using higher octane gasoline will not cause damage. However, the increase in octane number can 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 ratings, using lower octane gasoline 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 ignites, resistance will arise during the upward stroke. This resistance makes the engine run very unstably. 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, and in severe cases, cylinder scoring.
Let me share some experience. As a seasoned driver with years of experience, I've found that this issue really depends on your car model. For most vehicles, 92-octane gasoline is sufficient and more economical. 95-octane fuel has a higher octane rating and is suitable for high-performance engines, like some German cars or sports cars with high compression ratios. Using 92-octane in these vehicles can cause knocking and damage the engine. But don't just guess - the best approach is to check your owner's manual, which clearly states the recommended fuel grade. I drive a family SUV and have always used 92-octane without any issues, while my neighbor's BMW requires 95. The key is not to force lower-grade fuel just to save money, as saving small amounts now might cost you big on engine repairs later. Oh, and always pay attention to gas station quality - avoid roadside stalls as poor-quality fuel can be even more damaging to your car.
