Can I switch back to 92 after using 95 for half a year?
3 Answers
If the vehicle itself allows the use of 92-octane gasoline, you can switch back to 92. Below is relevant information about gasoline octane ratings: Relationship between octane rating and density: Different octane ratings have different densities. The density of 92-octane gasoline is approximately 0.72g/ml, while 95-octane gasoline has a density of about 0.725g/ml, and 98-octane gasoline is around 0.737g/ml. From this, it can be seen that the higher the octane rating, the greater the density of the gasoline. Relationship between octane rating and anti-knock performance: The reason gasoline has octane ratings is primarily due to the different anti-knock properties of various ratings. It is not that higher-octane gasoline has fewer impurities, but rather that higher-octane gasoline has better anti-knock performance. The higher the octane rating, the less likely the engine is to experience premature combustion during operation. Additionally, the compression ratio of the engine determines the required gasoline octane rating.
I've actually experienced this situation myself—after driving for half a year with 95, I wanted to switch to 92 to save some money. The first thing to do is check the owner's manual. Cars with high engine compression ratios must use 95, like turbocharged models. I specifically looked it up: the main difference between 92 and 95 is the octane rating, and the mixture blends quickly in the fuel tank. After switching back to 92, pay extra attention to the engine sound for the first two fuel tanks. If you hear a knocking sound like shaking beans, switch back to 95 immediately—it indicates engine knocking. After switching, my naturally aspirated car showed no change in power, and fuel consumption even dropped slightly. However, I noticed less explosive power when climbing hills on the highway compared to using 95.
Last time at the repair shop, the mechanic mentioned that as long as the car isn't picky, you can switch. The biggest concern when suddenly switching from long-term 95 to 92 is that lower-octane gasoline might not have enough anti-knock properties, causing the fuel to ignite before the piston fully compresses it, which can damage the engine. But if your car's manufacturer originally recommends using 92, and it's stated on the fuel cap or in the manual as '92 or above,' you can confidently make the switch. From my own experience, for the first 500 kilometers after switching, avoid aggressive acceleration to let the car's computer gradually adapt to the new fuel octane rating. This way, the ECU will adjust the ignition timing to match the anti-knock properties of 92.
