With the price of gasoline these days (over $3.00 per gallon as of this writing), most people
They are feeling the financial pressure and are wondering what they can do to reduce their gas costs. This article presents one of several ways to earn as many miles per dollar as possible.
When it comes to the grade of gasoline or octane number you put in your car, “more is better,” right?
Not always. There are a number of myths surrounding the use of high octane gasoline.
Myth #1: Using high octane gasoline will make my car run better.
Not quite. If your car is “pinging” or “thumping”, a higher octane gasoline will help or eliminate the ping and save your engine, but it doesn’t directly add power. However, it prevents your electronic ignition from delaying timing as an “anti-knock” measure when a ping is detected.
Myth #2: My car will get more miles per gallon if it uses higher octane gasoline.
Since a higher octane gasoline doesn’t make more power, you won’t get better gas mileage.
Myth #3: My engine will run cleaner and produce less emissions and smog with higher octane gasoline.
Is not true. Many oil company advertising methods may lead you to believe this, but octane has nothing to do with how “clean” your engine runs.
Myth #4 – Octane is added to gasoline to produce a higher quality fuel.
No, actually Octane. is Gasoline, at least for the most part. See octane rating below.
You can save money on gas simply by using the lowest octane gasoline your car will tolerate. Use a higher octane
gas from what the manufacturer says is simply a waste of money. If you are not sure what octane rating your car is designed for
use, you can start with the lowest octane (87 in most areas) and test it. If it pings under load, then go up to the
octane rating and only buy the lowest octane rating your car needs. To learn more about octane, keep reading.
What is “Pinging” or “Knocking”?
Most of us have heard the rattling under the hood, usually when the engine is under additional load like
climbing a hill, towing a boat or in a loaded truck. The noise itself is caused when the fuel-air mixture in the
the compression chamber ignites too soon (preignition or knock). This condition causes the fuel-air mixture to burn unevenly and
produces the sound of ping or knock. This uneven combustion causes flash points in the combustion chamber and can lead to engine damage.
What does octane do?
Without going into all the chemical properties and technical aspects, basically, octane raises the
burning point of gasoline when under compression and retards combustion. The result is that it does
the least volatile gasoline so it doesn’t ignite before your ignition system makes it fire at the correct time.
The intent of the octane rating is simply to provide an anti-knock property.
Octane Rating
The octane number you see at the gas pump is simply a percentage of the chemical octane number in the
gasoline blend In other words, if you buy gasoline with an 87 octane rating, that blend contains 87% octane and
the rest are lower quality chemicals like heptane. See also http://en.wikipedia.org/wiki/Octane_rating
What about “Octane Boost” additives?
If your car requires a higher octane gasoline, you can use “octane boosters” available at your local auto parts store. The cost
and effectiveness will vary. Test a full tank with an additive to see if your can works correctly, then do the math to see
does make sense. Here’s a cost analysis for my 1993 Mustang GT:
Example: 1 bottle of boost additive for a tank of gas costs about $5.00. With a 15-gallon tank, this adds about $.33 to the cost of each gallon of gas, plus the hassle of going to the auto parts store to buy it and remembering to add it at every fill-up.
If you really want or need a high octane mix, you may want to make your own.
homemade octane booster
There are a number of websites and blogs that post recipes or “homebrew”. I’m not going to post it here as I can’t directly endorse the
use or do-it-yourself safety. However, if you’re looking for a recipe to boost octane with xylene or toluene, you’ll find it there. The chemists
xylene and toluene are of higher “quality” and can produce an increase of more than 100%. The chemical octane alone, by definition, can never produce more than one
octane number greater than 100.
Other ping solutions
If your car continues to ping or knock even though you are using an octane rating of gasoline equal to or higher than that specified by your car manufacturer, this
it is an indication of engine problems that you should consult with your mechanic. There is a well known issue that you may be able to
try diagnosing yourself and that is the case for a stuck or faulty EGR valve. It is beyond the scope of this article to explain how to verify
its EGR valve, but it’s something to look into if your car has a chronic pinging problem.
