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The octane number of gasoline refers to the fuel’s ability to resist “knocking” or “pinging” during combustion, caused by the air/fuel mixture detonating prematurely in the engine. In general, higher-octane fuels resist knocking better than lower-octane fuels.

Detonation knock is a knocking noise that you’ll hear when the air/fuel mixture in the cylinders is detonating in more than once place at a time. Parts of the air/fuel mixture can start to ignite too early. When these mini fireballs collide, they create a knocking noise.

Detonation knock will damage your engine over time. It can cause cylinder temperatures to rise, which can lead to engine failure.

Detonation knock is more likely to occur in hot weather or if you’re using lower-octane fuel than what your car’s manufacturer recommends. That’s because heat and compression can cause the air/fuel mixture to detonate prematurely.

If you hear knocking, switch to a higher-octane fuel. You might also need to adjust the timing of your engine’s spark plugs. Consult your car’s owner’s manual or a qualified mechanic for more help.

Octane number – Conditional indicator of the anti-detonation properties of motor fuels. Engine fuel is compared to a mixture of isooctane (taken as 100) and H-Heptane (taken as 0). The percentage of isooctane in the mixture that is equivalent in detonation resistance to the fuel tested is called the octane number of the fuel. There are 2 methods of determination – motor and research.

To learn more about octane number, watch the video below.

What is fuel octane number?

Frequently Asked Questions (FAQ)

Octane number is a measure of the fuel’s ability to resist “knocking” or “pinging” during combustion. Knocking is an uncontrolled form of combustion that can cause severe engine damage if it occurs too frequently. A higher octane rating indicates better anti-knock properties and therefore higher quality gasoline. Gasoline with too low an octane rating may produce knocking and reduce engine performance. High-performance engines generally require higher octane fuels, with ratings of 91 or higher. However, using a fuel with too high of an octane for a particular engine could be wasteful as the additional properties would not be beneficial and could even cause damage due to increased combustion pressure.
David Muench (Carnes Mechanical)

David Muench (Carnes Mechanical)

Hey, I’m David. I’ve worked in a cars store for 6 years. I write reviews and guides, helping people to choose the most suitable technicals and best product for them. I’m happy to finally share my knowledge of the industry here, on CarnesMechanical.

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