What are the effects of switching from 98-octane gasoline to 95-octane?
1 Answers
When switching from 98-octane to 95-octane gasoline, it's important to note that occasional changes won't have any impact. However, long-term use of gasoline with different octane ratings can cause delayed ignition in the car's engine, meaning both the engine's power output and thermal efficiency will decrease. The practical experience is reduced power, which may lead to earlier major engine overhauls. You can decide which gasoline to use based on the engine's compression ratio. Cars with an engine compression ratio between 10.0 and 11.5 should use 95-octane gasoline. If the compression ratio is higher, 98-octane gasoline is recommended. However, with the use of new technologies, the compression ratio alone can no longer determine the appropriate gasoline grade. Engines with high compression ratios can also be tuned to use lower-octane gasoline because, besides the compression ratio, other factors such as ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Generally, the higher the gasoline octane rating, the higher the octane number and the better the anti-knock performance. 98-octane gasoline contains 98% isooctane and 2% n-heptane, while 95-octane gasoline contains 95% isooctane and 5% n-heptane. If you accidentally use the wrong gasoline grade occasionally, simply switch back to the correct one after refueling. However, long-term use of the wrong gasoline grade can have the following effects: Using a lower-octane gasoline in a high-octane vehicle may cause engine knocking. Since the octane number is significantly lower, the gasoline's ignition point decreases, leading to premature ignition during the compression stroke. If the fuel ignites before the spark plug fires, resistance will occur during the upward stroke. This resistance can make the engine run very unstable. If it's only mild knocking, the noise may increase 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, potentially leading to cylinder scoring in severe cases. When choosing gasoline, also consider the following: Select gasoline with appropriate volatility based on the ambient temperature. Gasoline with good volatility makes cold starts easier and allows the engine to warm up smoothly. However, if the volatility is too high, vapor lock may occur in the fuel lines, preventing the fuel pump from delivering gasoline properly and causing engine stalling. Choose gasoline based on its lead content. Determine whether your car is equipped with emission control devices such as a catalytic converter or oxygen sensors. If so, you must use unleaded gasoline to avoid damage to these devices and unnecessary additional repair costs.
