Save Money On Gas – The Octane Factor
With the price of gas these days (over $3.00 US per gallon at the time of this writing) most people
are feeling the economic pinch and wondering what they can do to trim their gas costs. This article presents one of several ways to get as many miles per buck as possible.
When it comes to the grade of gasoline or octane rating you put in your car, “More is Better” right?
Not always. There are several myths surrounding the use of high-octane gas.
Myth #1 – Using high-octane gas will make my car perform better.
Not exactly. If your car is “pinging” or “knocking”, a higher octane gas will help or eliminate the ping and save your engine, but it does not directly add horsepower. However, it does keep your electronic ignition from retarding the timing as an “anti-knock” measure when pinging is detected.
Myth #2 – My car will get more Miles Per Gallon by using a higher octane gas.
Since a higher octane gas does not produce more power, you will not get better gas mileage.
Myth #3 – My engine will run cleaner and produce less emissions and smog with a higher octane gas.
Not true. Many oil companies’ 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, Octane is the gasoline, at least most of it. See Octane Rating below.
You can save money on gas simply by using the lowest octane-rated gasoline that your car will tolerate. Using a higher octane
gas than what the manufacturer states is simply a waste of money. If you are not sure what octane your car is designed to
use, you can start with the lowest octane gas (87 in most areas) and try it. If it pings under load, then move up to the
next octane and only purchase the lowest octane grade that your car needs. For more information on octane, read on.
What is “Pinging” or “Knocking”?
Most of us have heard the rattling noise from under the hood, usually when the engine is under extra load like
climbing a hill, towing a boat, or in a loaded truck. The noise itself is caused when the air-fuel mixture in the
compression chamber ignites too soon (pre-ignition or detonation). This condition causes the air-fuel mixture to burn unevenly and
produces the ping or knock sound. This uneven burn causes flash points in the combustion chamber and can lead to engine damage.
What Does Octane Do?
Without getting into all of the chemical properties and technical stuff, octane raises the
combustion point of gasoline when under compression and slows the burning. The result is that it makes
the gasoline is less volatile so it does not ignite before your ignition system makes it fire at the correct time.
The intent of octane is simply to provide an anti-knock property.
Octane Rating
The Octane Rating you see at the gas pump is simply a percentage of the Octane Chemical in the
gasoline mixture. In other words, if you purchase gas with an 87 Octane rating, that mix contains 87% Octane and
the remainder is lower quality chemicals like heptane. Also see http://en.wikipedia.org/wiki/Octane_rating
What about “Octane Boost” Additives?
If your car requires a higher octane-rated gas, you can use off-the-shelf “Octane Boosters” from your local auto parts store. The cost
and effectiveness will vary. Try one tank full with one additive to see if you can run properly on it then do the math to see
if it makes sense. Here is a cost analysis for my 1993 Mustang GT:
Example: 1 bottle of additive to boost one 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 to purchase it and remembering to add it at each fill-up.
If you want or need a high-octane mixture, you may want to make your own.
Home-Made Octane Booster
Several websites and blogs publish the recipes or “home brew”. I am not going to publish it here as I cannot directly endorse the
use or safety of doing this yourself. However, if you search for an xylene or toluene octane boost recipe, you will find it out there. The chemicals
xylene and toluene are higher “quality” and can produce a boost of over 100%. The chemical Octane alone by definition, can never produce more than an
octane rating of more than 100.
Other Ping Solutions
If your car continues to ping or knock even though you are using an octane gas rated equal to or above what your car’s manufacturer specifies, this
is an indication of engine problems that you should have your mechanic look at. There is one well-known problem that you may be able to
try to diagnose yourself and that is the case of a stuck or failed EGR valve. It is beyond the scope of this article to explain how to check
your EGR valve, but it is something to look into if your car has a chronic ping problem.
