The Low-Down on High Octane Gasoline
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 owners manual
recommends offers absolutely no benefit. It wont make your car
perform better, go faster, get better mileage or run cleaner. Your
best bet: listen to your owners 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 gasolines 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.
Whats the right octane level for your car?
Check your owners 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 youre using the right octane level?
Listen to your cars engine. If it doesnt knock when you use the
recommended octane, youre 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 cars 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 wont harm your engine, and
doesnt indicate a need for higher octane. But dont 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
youre buying, check the octane rating on the yellow sticker on the
gas pump instead of relying on the name "premium" or
"regular."
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