What's the Difference Between Gasoline Grades?
3 Answers
Gasoline is currently classified into four grades: 89 (formerly 90), 92 (formerly 93), 95 (formerly 97), and 98 (a newly introduced grade). These numbers represent the octane rating of the gasoline, indicating its anti-knock properties, and are unrelated to the cleanliness of the fuel. It is more scientific and economical to refuel according to the engine's compression ratio or the requirements specified in the user manual, as this allows the engine to operate at maximum efficiency. During the design phase, car engines are configured to use a specific fuel grade based on their compression ratio. The compression ratio is a crucial structural parameter of an engine, defined as the ratio of the gas volume when the piston is at the bottom dead center (start of compression) to the gas volume when the piston is at the top dead center (end of compression). From the perspectives of power and fuel efficiency, a higher compression ratio is generally better. A high compression ratio improves power output, thermal efficiency, and enhances vehicle acceleration and top speed. However, the compression ratio of gasoline engines cannot be too high due to limitations in cylinder material properties and the risk of combustion knock. High-compression engines require high-octane fuel. Higher-octane fuels burn more slowly, reducing combustion knock, and are suited for engines with higher compression ratios. Conversely, lower-octane fuels burn faster, produce more combustion knock, and are suitable for engines with lower compression ratios. The fuel grade also affects the engine's ignition timing. Lower-octane gasoline burns faster, requiring retarded ignition timing, while higher-octane fuel burns slower, necessitating advanced ignition timing.
I often ponder about gasoline in the garage. First, the difference lies in the octane ratings, such as 92 or 95, which represent the level of octane. High-octane gasoline like 98 is more resistant to engine knocking, making it particularly suitable for high-performance models, such as turbocharged engines. Using lower-grade fuel in such engines may cause pre-ignition and damage components. For regular cars, 92-octane is sufficient and saves money. Another major difference is the composition—some fuels contain ethanol, like E10 ethanol gasoline, which is eco-friendly and reduces emissions but may corrode hoses in older cars or increase fuel consumption. Brands also differ; for example, Shell adds exclusive detergents to reduce carbon buildup and enhance performance, though it's pricier. I recommend checking the vehicle manual for the recommended fuel grade each time you refuel and avoiding the wrong type. Also, pay attention to the gas station's reputation—good stations offer purer fuel with fewer impurities, which helps maintain engine longevity. Seasons also play a role, as winter and summer gasoline formulations adjust for freeze protection or evaporation resistance. In summary, the differences stem from performance, environmental impact, cost, and compatibility, so it's essential to match your car's needs.
As a long-time car owner, I always pay attention to the differences in gasoline when refueling. The main distinctions are the octane ratings like 92 and 95; higher-octane fuels such as 98 provide smoother driving and slightly stronger power, but most regular cars don't need to waste money on them. In terms of price, 92 is the most economical, while 95 is slightly more expensive—filling up a tank can cost dozens of yuan more. There's also the distinction of ethanol-blended gasoline, like E10, which is more environmentally friendly and energy-saving but may result in slower acceleration and higher fuel consumption, making it less suitable for older cars. Different gas stations add different additives; for example, Sinopec's fuel might contain special cleaning components to reduce emissions. I often try different gas stations and find that major brands offer more stable fuel quality, reducing engine carbon buildup issues. I recommend that beginners start with the octane rating recommended in the manual and avoid switching arbitrarily, as engine problems can be costly and troublesome to repair. Additionally, gas prices in urban areas are often cheaper than in the suburbs, but the fuel quality is similar—weigh the pros and cons. In short, these differences affect driving experience, expenses, and vehicle health, so it's best to gradually figure out what works best for you.
