Which is better for car refueling, 92 or 95?
2 Answers
The octane rating of gasoline for a car should be based on the recommendation in the vehicle's official user manual. In addition to checking the appropriate gasoline grade in the user manual, you can also find it on the fuel tank cap, which will be clearly marked. Generally, the fuel grade can also be determined based on the engine's compression ratio. Cars with an engine compression ratio between 8.6-9.9 should use 92-octane gasoline, while those with a compression ratio between 10.0-11.5 should use 95-octane gasoline. If the compression ratio is higher, 98-octane gasoline is recommended. However, with the application of new technologies, the octane rating cannot be solely determined by the compression ratio. High compression ratio engines can also be tuned to use lower octane gasoline. This is because, apart from the compression ratio, other factors such as ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Generally, the higher the octane rating, the higher the octane number and the better the anti-knock performance. 92-octane gasoline contains 92% isooctane and 8% n-heptane, while 95-octane gasoline contains 95% isooctane and 5% n-heptane. Occasionally using the wrong gasoline grade only requires switching back to the correct grade after consumption. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended to use lower octane gasoline, using higher octane gasoline will not cause damage, but the increase in octane number may alter the fuel's ignition point, leading to delayed combustion in the engine. This means both the engine's power output and thermal efficiency will decrease, resulting in poorer performance. For vehicles recommended to use higher octane gasoline, using lower octane gasoline can cause engine knocking. Because the octane number is significantly lower, the reduced ignition point may cause premature ignition during the compression stroke. If combustion occurs before the spark plug ignites, resistance will arise during the upward stroke. This resistance can make the engine run very unstably. If the knocking is imperceptible, it may only increase noise without obvious damage to the engine. However, noticeable knocking indicates severe engine conditions, affecting not only driving stability but also causing abnormal wear on pistons and cylinders, and in severe cases, cylinder scoring.
As an average car owner, I prioritize fuel economy when purchasing a vehicle. 92-octane gasoline has always been my top choice because it's significantly cheaper—filling up a tank for daily commutes can save me dozens of yuan. Unless the car is a high-performance model or the manual explicitly specifies 95-octane, 92-octane is perfectly adequate. Most modern family car engines are designed to be compatible with it. While 95-octane might feel slightly smoother in terms of power, the difference is negligible and not worth the extra cost. In the long run, mistakenly using higher-octane fuel could increase carbon buildup risks, potentially shortening engine life. My advice is to choose based on your budget—saving money isn't shameful. Stick with 92-octane when appropriate and allocate the savings to other maintenance needs, like oil changes. Ultimately, following the manufacturer's recommendation is the wisest approach—don't blindly upgrade fuel grades just because others do.
