Monday, May 2, 2011

Trophy Wife Talks Cars: Octane levels

I have really wanted to put up my huge rant on gas grades for months now.  With the price of gas getting higher and higher, it is an important subject.  I am so tired of hearing ignorant men at the gas station claiming don't use ethanol because you're just burning it up faster and other nonsense.  So let's talk gas.

The one very important thing to remember is that it doesn't matter if you use 'premium' or 'mid-grade' fuel in your car.  What matters at the pump is the octane levels.  That is the key factor in picking your fuel grade.  Basic gasoline is made from the same stuff.  The different brands use different additives.  Over the years, some gasoline companies have started decreasing the quality and amount of it's additives.  This causes build up and emissions problems, which can lead to problems for you in the long run.  It's important to use a 'top tier' gas.  This is another topic for another day though, but feel free to check it out.

Octane ratings show at what pressure your gas will combust without a spark; this is called pre-ignition or detonation.  Your car's computer can sense this and it will retard the mileage to save your engine from potential damage.  What makes this an important factor is that when your engine fuel ignites without a spark, it throws off the rhythm in how your engine runs and will result in a knock, or a rough sound.  This causes your engine to not running efficiently.  The higher the octane rating, the higher rate of compression needed for the fuel to spontaneously combust.  So, if you have a high performance engine (which most cars don't), you need to have a higher grade octane level because that engine will compress at a higher rate.  Otherwise, it will affect the performance of your engine, like how it accelerates from a stop.  This doesn't necessarily mean that you will burn more fuel, it just means that your car won't perform up to it's full potential.  On the other hand, if you have a regular engine and you put a higher octane level in it, this will not make that engine perform better.  That engine can only perform to the standard that it was built.  (I will someday write a post about suck, squeeze, pop, phooey; if anyone is interested about learning how an internal combustion engine works.)

Basically, you just need to use the octane level that is recommended for your car's particular engine.  The easiest way to find this is in the owner's manual.  (Yes, they are meant to be read and they are full of great information, like maintenance schedules.)  Some cars even have the recommended octane level on a sticker near the gas cap.  You can also Google your vehicle Year, Make and Model Owner's Manual to find the manual online.  Here is what my owner's manual says.
It ends by saying 'recommended, see your local dealer or repair facility."

So, you are doing yourself no favors if you are using 'Premium' fuel if you don't drive a Viper, a Corvette, or other High Performance vehicle.  The only exception to this is if you have an ASE Certified, trained technician who is reputable tell you that on your particular vehicle, it would benefit from having a higher octane level to help reduce knock and wear on your particular engine to help resolve problems that you are having.

I would be wary of people who caution you against using ethanol or mid-grade fuels in your truck, car or van.  Do a little research.  Ask your personal Independent Automotive Technician your questions; they will be glad to answer them.

Later on, I will tell you about different ways to help increase your fuel efficiency and get the most 'bang' for your buck.

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  1. Thanks for the great info! I am going to share this on my fan page on Facebook. I hope you don't mind. I also hear so often "don't use ethanol" for various reason and it drives me nuts! I had one guy tell me this while I was pumping my gas. I may be a chick, but I'm not lame when it comes to the pump!


  2. Thanks Vanessa!! I too have had 'know-it-all' men approach me while pumping to tell me I shouldn't use ethanol too. I tell them that if they want to pay for it, I'll use whatever they want. Then they usually leave me alone. If they don't, then I love to stretch my car knowledge legs and tell them all about what's under the hood of what they are driving and what they can do to help their cars run more efficiently. When they realize that I know just as much (or more) than they do, they usually go away with their tails between their legs. ;)


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