Can 98 and 95 gasoline be mixed?
2 Answers
95 and 98 gasoline cannot be mixed, as mixing them can cause engine knocking. Gasoline is a mixture, and while the chemical compositions of the two are relatively similar with strong anti-knock properties, it is recommended to use them separately to ensure vehicle safety. The difference between 98 and 95 gasoline lies in their octane ratings and quality levels. The specific details are as follows: Different octane ratings: 92 gasoline contains 92% isooctane and 8% n-heptane. 95 gasoline: consists of 95% isooctane and 3% n-heptane. Different gasoline quality levels: The gasoline grade represents the octane rating of the fuel. A higher grade indicates a higher octane rating, which means better anti-knock performance. This results in smoother engine operation, reduced vehicle wear, and better engine protection. It is suggested that using a higher-grade gasoline in a vehicle designed for a lower grade will not cause damage, but the increase in octane rating 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. Using lower-grade gasoline in a vehicle designed for a higher grade can cause engine knocking. A significantly lower octane rating reduces the gasoline's ignition point, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires, resistance will arise during the upward stroke, making the engine run very unstably. Mild knocking may only increase noise without obvious engine damage, but noticeable knocking indicates severe engine conditions. The vibration affects not only driving stability but also causes abnormal wear on pistons and cylinders, and in severe cases, cylinder scoring.
Last time on a long drive, I encountered a gas station that only had 98-octane fuel, so I temporarily mixed it into my 95-octane car. The experienced attendant said occasional mixing won’t harm the car, as the difference in anti-knock properties isn’t too significant, and the ECU will automatically adjust the ignition timing. However, long-term mixing might overwork the sensors—like a person constantly wearing ill-fitting shoes. Now, I stick to 95-octane whenever possible and only mix when absolutely necessary. Afterward, I gradually switch back to pure 95 over the next two or three fill-ups to give the engine a breather. After all, as the mechanic said, precision engines like those in European cars are better off without random fuel mixing.
