Car plus 95 is quieter because knock is reduced.
First of all, car 92 uses 95% gasoline, which is relatively quiet to drive. The main reason is that the knock noise becomes smaller. Mi published a paper "Discussion on Noise Pollution of Automobile Engine and Its Control" in the magazine "Internal Combustion Engine and Accessories", which said. When surface ignition or knocking occurs inside the cylinder block, knocking noise will be generated. 95% gasoline and 92% gasoline have higher octane number and better antiknock performance, which can reduce or inhibit knocking, thus reducing noise.
There is no need to add 95 to reduce the noise.
Jia Dairun of Zhejiang University has a master's thesis "Research on Multi-objective Optimization Scheme of Electronic Control Gasoline Engine Calibration System and Ignition Advance Angle", which has been mentioned above. The ignition matching standard of the engine is to avoid knocking, which is embodied in: strong knocking does not occur at medium and low loads, and knocking cannot occur at high loads.
To put it simply: the 92 car itself is an ignition system set according to the No.92 gasoline label, and knocking should have been effectively suppressed. But if the car is really old, it was young before, wasn't it? It sounds a bit like a tractor in the back. It's loud, and the carbon deposit is much older, right?
92 plus 95 may even improve the knock noise, and you may feel it. Yang Qi of Jilin University also has a master's thesis "Research on Control and Evaluation Methods of Engine Carbon Deposition", which also says.
A large amount of carbon accumulates in the combustion chamber of classic cars, which will reduce the volume of the combustion chamber and lead to a larger compression ratio. When working under high load, it is easier to produce premature combustion and deflagration, which is often called "knocking" in local dialect.
At this time, the original 92 was changed to 95. Because the antiknock performance of gasoline has improved a little, I really feel that the engine may be quieter and the car will drive better. Of course, the price of oil is also higher.