Can You Add 95 Octane Gasoline After Using 92 Octane?
4 Answers
If the user manual indicates that the minimum octane rating required is 92, then using 95 octane gasoline is acceptable. However, if the manual specifies 95 octane gasoline, you should not use 92 octane. Below are some relevant details: 1. The primary difference between 92 and 95 octane gasoline lies in the ratio of heptane and isooctane. 92 octane gasoline contains 92% isooctane and 8% heptane, while 95 octane gasoline contains 95% isooctane and 5% heptane. 2. The octane rating does not reflect the purity or quality of the gasoline. In fact, the octane number only indicates the gasoline's resistance to knocking and has little to do with its overall quality. If your car can use both 92 and 95 octane gasoline, it is not recommended to alternate between different octane ratings, as this may adversely affect the engine. It is best to consistently use one type of octane gasoline.
Last time when my car was almost out of gas, the 92-octane pump at the gas station was under maintenance, so I directly filled half a tank with 95-octane. Actually, mixing gasoline isn’t a big issue. The main difference between 92 and 95 is the octane rating and anti-knock performance. 95 has better anti-knock properties, but your car originally designed for 92 has an engine compression ratio tailored for 92. After mixing, the system can automatically adjust the ignition timing to adapt, so it won’t harm the engine. It’s fine occasionally, just remember not to mix them long-term, otherwise fuel consumption might increase by about 0.5, and more deposits may accumulate in the tank. The safest approach is still to follow the fuel grade recommended in the manual, as manufacturers have tested it over tens of thousands of kilometers before making the recommendation.
Once on the highway, my fuel gauge was almost empty, and the service area only had 95-octane gas. I reluctantly added 10 liters to my 92-octane tank. I asked a mechanic, and he said mixing them just averages the octane to around 93. Short-term, it doesn’t harm the car since modern engines have knock sensors that adjust automatically. But long-term mixing isn’t ideal, especially for older cars with worn piston rings, as it can lead to carbon buildup. Also, consider the tank material—metal tanks handle mixed fuels better than plastic ones against corrosion. He advised running this tank empty before switching back to 92 and avoiding mixing more than three tanks in a row.
Previously, my neighbor accidentally filled his car, which normally takes 92 octane, with 95 octane gasoline, and it ran just fine. The base oils of the two fuels are quite similar, with the main difference lying in the additive ratios. Mixing them is essentially like creating a homemade 93 octane blend. As long as you don't mix diesel and gasoline, there's no danger—the engine's computer will adjust the ignition parameters accordingly. However, it's advisable not to fill up too much. For instance, when half a tank of 92 octane remains, adding no more than 200 yuan worth of 95 octane is recommended to avoid excessive deviation in octane levels. Additionally, pay attention to the quality of the gasoline at the station; substandard 95 octane from small stations can be more harmful to your car than regular 92 octane from reputable ones. It's also a good idea to keep track of the amount of fuel added, making it easier to switch back to the original octane rating next time for peace of mind.
