Can a Car Specified for 95 Octane Use 92 Octane Gasoline?
2 Answers
You should refuel according to the specified requirements. Occasionally using the wrong gasoline octane rating only requires switching back to the correct octane rating after consumption. However, prolonged use of the wrong octane rating can have the following effects: For vehicles recommended for lower octane ratings, using a higher octane gasoline will not cause damage, but the increase in octane value will 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 in practice. For vehicles recommended for higher octane ratings, using a lower octane gasoline can cause engine knocking. Because the octane value is significantly lower, the gasoline's ignition point decreases, causing premature ignition during the compression stroke. If the fuel combusts before the spark plug fires during the compression stroke, resistance will occur during the upward stroke. This resistance makes the engine run very unstably. If it's mild knocking, it only increases noise without significant engine damage. 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. Besides checking the appropriate gasoline octane rating in the car's manual, you can also find it on the fuel tank cap, which usually specifies the required octane. Typically, the gasoline octane rating can also be determined based on the engine's compression ratio. Cars with a 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 application of new technologies, the octane rating can no longer be solely determined by the compression ratio. High compression ratio engines can also be tuned to use lower octane gasoline because factors like ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Generally, the higher the gasoline octane rating, the higher the octane value 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.
Never use 92 octane gasoline in a car that requires 95. When I drove an old German car, I foolishly filled it with 92 to save a few bucks, and the engine started knocking constantly. Within a month, there was a noticeable drop in power. The mechanic said the detonation had damaged the cylinder head, costing me thousands in repairs. High-compression engines are designed for higher octane fuel—92 is too low and can cause abnormal combustion. Long-term use might even affect the electronic control module. The manual clearly states the risks of using lower-grade fuel, including voiding the warranty. Now I only use 95 octane—protecting the engine actually saves money in the long run. The price difference is minimal, and safety comes first.
