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Which Grade of Gasoline Should You Use? Is There A Difference?



very time you go to the gas station and fill up, you’re faced with an important decision-what type of gasoline is right for your car? Should you choose one with higher octane or not? In this article, we will discuss gasoline, which grade of gasoline you should you use for your car, and whether there is a difference between the various types. 


As you might know, gasoline is a mixture of hydrocarbons and it is commonly used as fuel in spark ignition engines. The gasoline is mixed with air and is sprayed into the engine. The heat in the engine turns it into a vapor. A spark plug then sets off a spark that burns the mixture. Additives are added to gasoline to make it burn better. However, sometimes there are problems with this procedure. Sometimes, the gasoline mixture may get ignited before it should. This leads to the engine making an unusual sound, usually called a knock. Different kinds of gasoline are differentiated according to the probability of engine knocking. They are rated by an octane number.


The word octane comes from iso-octane, a hydrocarbon liquid that is used as a measuring standard of gasoline’s anti-knock qualities. A gasoline that has a mixture of 90 percent iso-octane and 10 percent N-heptane is said to have an anti-knock index, or octane rating of 90. Many regular gasolines have octane ratings of 90. Adding more octane to fuel will further prevent it from burning. This means that fuel with less octane will burn faster than a fuel with high octane rating.


But, what does this mean for you, the consumer? Well, based on the octane ratings, Gasoline is classified into three grades-regular, mid-grade, and premium.

Regular gasoline has an octane rating, greater than or equal to 85 and less than 88.

Mid-grade gasoline has an antiknock index, or octane rating, greater than or equal to 88 and less than or equal to 90 is classified as mid-grade gasoline.

Premium gasoline has an octane rating, greater than 90.

In determining what type of grade is best suited for your particular engine, you must consider numerous factors.

·         Higher octane rating does not mean that it is best suited for the automobile. A higher level of octane is added basically to prevent engine knocking. For example, in order to drive at high altitude places, high octane rating is not required. In this case, using a fuel with higher octane rating will add to the operating cost as higher octane rated fuels cost extra.

·         Cars that have bigger and powerful engines need high-octane levels in the gas. This is due to the fact that the engine is under high pressure and chances of knocking increase. However, if we use premium gasoline in a car which does not have a high performance engine, the fuel might not burn properly, since premium gasoline is harder to burn. This will lead to carbon deposits on the engine leading to engine clogging. This would further reduce the miles per liter and can prove very harmful in the long run. It may also increase emission levels and can cause deposits on the catalytic converter. This would be a big price to pay for a fuel that costs more and believed to be a better one.

So, in a nutshell:

·         Lower octane fuel can be used while traveling in the hills, however please refer to the engine specifications prior to taking a decision.

·         Do not use high-octane fuel for old cars, or cars having less power.

·         Premium gasoline is recommended for engines that perform better in terms of power.

Finally, refer to your specific engine specifications prior to choose the right kind of fuel for your particular automobile.


Also see

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Finding a Good Mechanic Doesn't Have to Give You a Headache -part 3 in a series.

Three Reasons Why Your Car May Not Start -Can't get the car out of your driveway?  Read on!

Fuel and Induction System Cleaning-get real benefits for fuel economy, engine performance and lower emissions.




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