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Feature
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Written by Sabrina Deparine
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Monday, 06 July 2009 11:43 |
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Page views: 2263 |
All gasoline products in the market have octane ratings and with the recent release of Seaoil’s Extreme 97 gasoline that boasts of 97 octane rating (the highest, by far, in the Philippine market), a lot of people have probably become more curious now with what octane is.
• What is octane?
Octane is oftentimes defined along the lines of internal engine combustions. During the internal combustion process in an engine, gasoline is mixed with air and then compressed. This compressed gasoline-air mixture has a tendency to combust or ignite prematurely instead of burning smoothly. This premature ignition cause engine knock, a rattling sound in one or more of the car cylinder.
• What is knocking and is it harmful for the engine?
Knocking refers to the rattling of the piston in the engine cylinder due to the early or premature ignition of the fuel mixture so that it pushes against the piston while the piston is going upwards and the uneven combustion of the gasoline-air mixture in which it ignites earlier on only one side of the piston while the mixture on the other side has not ignited yet.
Actually, occasional or light knocking is not harmful and is not an indication of the need for high octane fuel. However, frequent and harder knocking should be addressed immediately because it might cause some engine damage.
• Is high-octane fuel better than low-octane fuel?
This depends on the car model. High octane fuel is more recommended for older cars with carbureted engine because the high octane can help regulate the gasoline-air mix. In fact, the notion that “high octane is better” started in older times when car engines had carburetors. Technically, older engines are not capable of regulating the gasoline-air mixture that goes into the engine. Also, the carburetor may also be a source of problem. For instance, if the carburetor needs to be adjusted, this may cause the engine system to mix too much fuel with the air. This is disadvantageous because it means that the fuel will not burn completely. The excess gasoline in the mixture will go into the carbon deposits and may become the cause of premature ignition due to the heat of the engine cylinders.
Newer car models particularly those with high-performance engine require high-octane fuel. This is because high-performance engines have high compression ratios that increase the tendency for pre-ignition or engine knocking. It also causes the fuel to burn more quickly.
High-octane fuel is also recommended for vehicles that are driven on roads that require much acceleration and power. Of course, high octane fuel is recommended when the car engine knocks frequently.
• How do oil companies improve the octane of their gasoline products?
The octane of a particular gasoline product may be enhanced using gasoline additives like tetra-ethyl lead, methyl tert-butyl ether (MTBE), and toluene.
• What is octane rating?
Octane rating pertains to the resistance of the gasoline to engine knocking or detonation especially during internal combustion.
• How is octane rating assigned?
A particular gasoline product is assigned an octane rating after it is tested and compared to a mixture of iso-octane and n-heptane chemicals. Iso-octane is assigned an octane rating of 100 while n-heptane is assigned an octane rating of zero. For example, E10 gasoline has an octane rating of 95. This means that E10 exhibits the same detonation resistance properties as the mixture containing 95% iso-octane and 5% n-heptane.
• Is octane rating associated with the energy content of the gasoline?
No, the octane rating of a gasoline product is not associated with its energy content. The octane rating is only the measure of the gasoline product’s tendency to resist engine combustion.
High octane ratings are usually correlated to higher activation energies of the gasoline. Activation energy refers to the amount of energy required to start and proceed a chemical reaction.
So now you know what octane and its effects are. The next time you load gasoline in your car, keep an eye on the octane rating.
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