What is the Difference Between High and Low Gasoline Octane Ratings?

[Lois]

Gasoline octane ratings are determined by the octane number of the gasoline. The higher the octane number, the stronger the anti-knock capability of the gasoline, and the higher the octane rating. The anti-knock performance indicator of gasoline is called the octane number, which is the gasoline octane rating. Generally, engines with high compression ratios require gasoline with higher octane ratings, while engines with low compression ratios use gasoline with lower octane ratings to ensure normal vehicle operation. Below is a related introduction: 1. Principle: Generally, engine operation consists of a repetitive cycle of "intake-compression-combustion-exhaust-intake" in the cylinders. The compression ratio is the ratio of the cylinder volume when the piston is at the farthest and nearest points in its stroke. The best way to reduce fuel consumption costs is to increase the engine's compression ratio. Increasing the compression ratio can alter the piston stroke, compressing the air-fuel mixture more intensely, which results in a stronger combustion reaction and more complete combustion. However, the compression ratio of a car is not easily changed and is matched with an indicator, namely the gasoline's anti-knock performance indicator, known as the octane number, which is the gasoline octane rating. 2. Composition of gasoline: Standard gasoline consists of isooctane and n-heptane. Isooctane has excellent anti-knock properties with an octane number of 100, while n-heptane has poor anti-knock properties and is prone to knocking in gasoline engines, with an octane number of 0. Generally, if a gasoline's octane rating is 0, it means the gasoline contains 90% isooctane and 10% n-heptane.

[DelSawyer]

Gasoline octane ratings primarily indicate differences in anti-knock properties, with higher octane fuel offering better resistance to engine knocking. Simply put, high-compression engines require higher octane fuel—many turbocharged models need 95 octane or above. Using lower octane can cause knocking and piston slapping sounds. In my decade-plus as a mechanic, I've seen many owners use the wrong fuel, resulting in increased carbon deposits and reduced power. Lower octane fuel suits naturally aspirated engines better, being more economical. Always check your owner's manual before refueling—don't compromise for savings or prestige. Remember, octane rating doesn't correlate with cleanliness—Sinopec's 92 and 98 octane fuels contain similar detergent additives. The key is matching your engine's compression ratio. Long-term use of incorrect fuel may damage piston rings, leading to repairs costing thousands.

[LylaRose]

I have a deep understanding of gasoline octane ratings, as my two family cars use different grades. The numbers 92, 95, and 98 don't indicate fuel quality differences—the core factor is how the octane rating affects anti-knock performance. Higher-octane fuel withstands compression better, which is why high-displacement track cars need 98-octane to perform at their peak. For regular cars, there's no need to use premium fuel. I've tested the same car with both 92 and 95 octane—the cost difference was 0.3 RMB per kilometer with virtually no power difference. Forcing high-octane fuel into a low-compression engine can actually lead to incomplete combustion and clogged fuel injectors. Gas station attendants always remind us to check the fuel cap label—if the manufacturer specifies 92-octane, don't arbitrarily switch to 95. With fuel prices so high, choosing the right octane rating is the most practical way to save money.

[StMicah]

Let's start with the basics of engine principles when talking about gasoline octane ratings. Higher compression ratios require higher-octane fuel to prevent knocking, just like my modified GK5 - when the compression ratio reached 11.5, I switched to 95-octane. The octane number represents the percentage of anti-knock components, so 92-octane means it contains 92% anti-knock additives. Using higher octane doesn't mean cleaner fuel - the filtration system is what really matters. Occasionally mixing different grades is fine, but avoid long-term use of incorrect fuel, especially for turbocharged cars where low-octane fuel can trigger warning lights. I always follow the manufacturer's recommended octane rating since modern cars have knock sensors that can adjust ignition timing. As long as you don't consistently use the wrong fuel, it won't cause major issues. Remember, your octane choice directly affects engine longevity.

[JacksonMarie]

The main difference between gasoline grades lies in their anti-knock capability. High-grade fuel is suitable for high-performance vehicles, like my old Crown with a compression ratio of 9.8 that runs perfectly on 92 octane, while the newly purchased Audi A4 requires 95 octane. Practical tests show consequences of using wrong fuel: when lower-grade cars use 95 octane, black smoke immediately comes out of the exhaust pipe during cold starts; high compression ratio vehicles using 92 octane produce noticeable knocking sounds. Three points to note when refueling: check the manual for specified grade, look at the fuel cap label, and don't listen to gas station promotions. Actually, the octane rating has nothing to do with gasoline cleanliness - Sinopec's 92 octane contains more detergents than some private stations' 98 octane. For daily drivers, using the correct grade consistently protects the engine better than chasing premium fuels.