gasoline octane facts
High Octane fuels and you
Are you tempted to buy a high octane
gasoline for your car because you want to improve its
performance? If so, take note: the recommended gasoline
for most cars is regular octane. In fact, in most cases,
using a higher octane gasoline than your owner's manual
recommends offers absolutely no benefit. It won't make
your car perform better, go faster, get better mileage
or run cleaner. Your best bet: listen to your owner's
manual.
The only time you might need to switch
to a higher octane level is if your car engine knocks
when you use the recommended fuel. This happens to a
small percentage of cars.
Unless your engine is knocking, buying
higher octane gasoline is a waste of money, too. Premium
gas costs 15 to 20 cents per gallon more than regular.
That can add up to $100 or more a year in extra costs.
Studies indicate that altogether, drivers may be spending
hundreds of millions of dollars each year for higher
octane gas than they need.
What are
octane ratings?
Octane ratings measure a gasoline's ability to resist
engine knock, a rattling or pinging sound that results
from premature ignition of the compressed fuel-air mixture
in one or more cylinders. Most gas stations offer three
octane grades: regular (usually 87 octane), mid-grade
(usually 89 octane) and premium (usually 92 or 93).
The ratings must be posted on bright yellow stickers
on each gasoline pump.
What's the
right octane level for your car?
Check your owner's manual to determine the right octane
level for your car. Regular octane is recommended for
most cars. However, some cars with high compression
engines, like sports cars and certain luxury cars, need
mid-grade or premium gasoline to prevent knock.
How can you tell if you're using the
right octane level? Listen to your car's engine. If
it doesn't knock when you use the recommended octane,
you're using the right grade of gasoline.
Will higher
octane gasoline clean your engine better?
As a rule, high octane gasoline does not outperform
regular octane in preventing engine deposits from forming,
in removing them, or in cleaning your car's engine.
In fact, the U.S. Environmental Protection Agency requires
that all octane grades of all brands of gasoline contain
engine cleaning detergent additives to protect against
the build-up of harmful levels of engine deposits during
the expected life of your car.
Should you
ever switch to a higher octane gasoline?
A few car engines may knock or ping - even if you use
the recommended octane. If this happens, try switching
to the next highest octane grade. In many cases, switching
to the mid-grade or premium-grade gasoline will eliminate
the knock. If the knocking or pinging continues after
one or two fill-ups, you may need a tune-up or some
other repair. After that work is done, go back to the
lowest octane grade at which your engine runs without
knocking.
Is knocking
harmful?
Occasional light knocking or pinging won't harm your
engine, and doesn't indicate a need for higher octane.
But don't ignore severe knocking. A heavy or persistent
knock can lead to engine damage.
Is all "premium"
or "regular" gasoline the same?
The octane rating of gasoline marked "premium"
or "regular" is not consistent across the
country. One state may require a minimum octane rating
of 92 for all premium gasoline, while another may allow
90 octane to be called premium. To make sure you know
what you're buying, check the octane rating on the yellow
sticker on the gas pump instead of relying on the name
"premium" or "regular."
For More
Information
If you're concerned about the accuracy of an octane
label - or if you don't see a yellow octane sticker
on a gasoline pump, write: Consumer Response Center,
Federal Trade Commission, Washington, DC 20580.
facts sources:
http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm
