Will using 95-octane gasoline improve the power of the Sylphy?
3 Answers
The power of a Sylphy car using 95-octane gasoline will not significantly improve, and the effect is not noticeable. According to the official car manual recommendation, the Sylphy should use 92-octane gasoline. If the Sylphy occasionally uses the wrong gasoline grade, simply switch back to the correct gasoline grade after use. However, if the wrong gasoline grade is used for a long time, the following effects may occur: For vehicles recommended for low-octane gasoline, using a higher-octane gasoline will not cause damage, but the increase in octane rating will change the ignition point of the fuel, leading to delayed combustion in the engine. This means the engine's power output and thermal efficiency will decrease, and the actual feedback is a decline in power. For vehicles recommended for high-octane gasoline, using a lower-octane gasoline may cause engine knocking. Because the octane rating is too low, the ignition point of the gasoline decreases, causing it to ignite prematurely during the compression stroke. If the fuel ignites before the spark plug fires during the compression stroke, resistance will occur during the upward stroke. This resistance will make the engine run very unstably. If the knocking is mild, it may only result in increased noise with no significant damage to the engine. However, if the knocking is severe, it indicates serious engine conditions, affecting not only driving stability but also causing abnormal wear on the pistons and cylinders, and in severe cases, cylinder scuffing. In addition to checking the appropriate gasoline grade in the car manual, the Sylphy's recommended gasoline grade can also be found on the fuel tank cap. Usually, the gasoline 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. However, with the use of some new technologies, the gasoline grade cannot be determined solely based on the compression ratio. A high compression ratio can also be adjusted to use low-octane gasoline because, in addition to the compression ratio, other factors such as ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Generally, the higher the gasoline grade, the higher the octane rating 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.
I've been driving a Sylphy for over a decade and specifically tested this issue. The Sylphy's engine compression ratio is 9.8:1, and the manufacturer specifies that 92-octane fuel is perfectly adequate. While using 95-octane gasoline does improve anti-knock performance, the power increase is barely noticeable. Nissan's MR engine ECU automatically adapts to different fuel grades, but the tuning prioritizes fuel economy. Last month, I ran the same highway route twice - the 95-octane fuel actually consumed 0.3 liters more per 100km. Unless you've reprogrammed the ECU to increase compression ratio, there's really no need to spend extra. What's more important is not waiting until the fuel light comes on to refuel - the fuel pump's cooling relies on gasoline immersion, and frequently running on low fuel will shorten the fuel pump's lifespan.
Having repaired Nissan cars for eight years, this is a common question from customers. For naturally aspirated cars like the Sylphy, using higher-octane fuel has limited effects. 95-octane fuel has a higher octane rating and better anti-knock properties, making it suitable for turbocharged cars or high-compression engines. However, the Sylphy's compression ratio is less than 10:1, and its ECU's ignition timing is set conservatively. I've tested the data logs and found that the fuel injection pulse width doesn't change at all when using 95-octane fuel. The only noticeable differences are slightly reduced engine noise during cold starts and a psychological feeling of smoother throttle response. If you really want to improve performance, it's better to replace the air filter regularly or use a proper fuel additive to clean carbon deposits.
