According to the experts, premium gas run in engines designed for regular
gas does not improve performance and will actually hurt performance. While
there are some people who swear the engine runs better using premium, the
experts say they must have smoked too much pot and have fried their brain
cells.


Why use premium gas when regular will do?
By James R. Healey, USA TODAY
Marti Mayne once fueled her low-octane Subaru with high-octane gas. Not now.
Premium-gas prices "went sky high, and now I just use low grade" to motor
around Yarmouth, Maine, where she runs a marketing business.

Cost differences between regular and premium is as plain as, well,
the sign at the station, like this one in Chicago.
By Scott Olson, Getty Images

When prices dropped earlier this year, she stuck with cheaper fuel because
"I don't think that my car runs any differently on high, medium or lower
grade."

She's right. Engines designed for regular fuel don't improve on premium and
sometimes run worse. And today's engines designed for premium run fine on
regular, too, their makers say, though power declines slightly. (Background:
About Octane ratings)

But premium lovers are passionate. "I would simply curtail driving rather
than switch grades," says Bill Teater of Mount Vernon, Ohio, who puts
high-test in both his Cadillacs, though only one recommends it. He's sure
both the DeVille and the Escalade run rough and lack pep on regular.

Prejudice and preference aside, engineers, scientists and the federal
government say there's little need for premium.

When fuel's cheap, motorists are willing to pay 20 cents or so more for
premium. But as gas prices sneak back up, the mental wrangle begins anew
over whether it's OK to burn cheaper, regular-grade gas.

AS PRICES RISE, CONSUMERS
SHUN PREMIUM GAS
Average price of a gallon of premium gasoline:
1993 $1.30
1999 $1.36
2002 $1.58
20031 $1.80
Premium gas share of all gas sold:
1993 19.9%
1999 16.8%
2002 13.5%
2003 12.1%
Sources: Energy Information Administration,
American Petroleum Institute






The answer almost always is yes.

"I personally use regular even though my owner's manual says you'll get
better performance with premium," says Lewis Gibbs, consulting engineer and
45-year veteran at Chevron oil company. He's chairman of Technical Committee
7 on Fuels, part of the Society of Automotive Engineers (SAE) Fuels &
Lubricants Council. Gibbs knows gas.

"My wife runs midgrade (89 octane) in her car, and it's a turbocharged
engine" meant for 91-octane premium, he says.

Premium - gasoline having an octane rating 91 or higher - is just 12.1% of
sales this year, down from 13.5% in 2002, when it was 22 cents a gallon
cheaper, and well below the modern high of 20.3% in 1994, when it was 49
cents cheaper, according to industry and government data. Despite the allure
of premium, once they abandon it, most motorists don't come back, the data
suggest.

For every dime increase in the price, sales of premium gas drop 1%, Bob
Johnson, general manager of gasoline and environmental services for the
7-Eleven chain, figures, based on data back to 1998.

The main advantage of premium-grade gas is that it allows automakers to
advertise a few more horsepower by designing and tuning engines to take
advantage of premium's anti-knock properties. But auto engineers generally
agree that if you use regular in a premium engine, the power loss is so
slight, most drivers can't tell.

"I go back and forth, and I'm hard-pressed to notice" whether there's
regular or premium in the tank, says Jeff Jetter, principal chemist at Honda
Research and Development Americas. He drives an Acura designed for premium.

Import brands, especially, use premium fuel to distinguish their upmarket
models. Most Toyotas, for instance, are designed to run on regular or
midgrade, while the automaker's Lexus luxury brand prefers premium. Same
with Honda and its Acura luxury line.

"Generally, the more expensive the vehicle, the higher the expectation for
performance and the more the customer is willing to pay for fuel," says Pete
Haidos, head of product planning for Nissan in the USA.

Actually, the price debate is nearly worthless. At 20 cents more for
premium, pumping 20 gallons of it instead of regular would cost $4 more.
Annually, that's a difference of $171 for a vehicle that averages 14 miles
per gallon - as some big sport-utility vehicles do - and is driven 12,000
miles a year.

Gasoline retailers and refiners like high-test because it's more profitable
than regular-grade gas is. The retailer paid about 8 cents more for the
premium you pay 20 cents more for - though that margin can swing wildly.
Refiners make a few cents a gallon more on premium than on regular when they
sell to wholesale distributors.

As long as it's clean

Profit is meaningless to the modern engine, which, regardless of what's
specified in the owner's manual, hardly cares what you use - as long as it's
clean.

Today's engines use highly evolved versions of a device called a knock
sensor to adjust settings automatically for low-octane gas. And more engine
control computers have adequate memory to allow separate sets of
instructions for various octanes. The engine control computers keep pushing
to maximize performance on whatever grade of fuel is used.

Extreme pressure inside the cylinders causes knock, which is the sound of
the pistons literally rattling inside the cylinders. Too much too long can
damage the engine. A little now and then won't.

The only modern engines that should really need premium are those with
superchargers, which force-feed fuel into the cylinders. "You're driving
along and just tramp the gas and the knock sensor cannot sense the knock
fast enough in some cases," because the supercharger boosts pressure so
fast, says Bob Furey, chemist and fuels specialist at General Motors.

Burning regular when the owner's manual specifies premium won't void the
warranty, nor damage the engine, even the most finicky automakers say.
"You're giving up perhaps just a little bit of performance that a customer
wouldn't really even notice, it's so slight," says Furey.

Automakers say they don't test premium engines on regular to check the
difference, but some auto engineers estimate that power declines roughly 5%.

"We can't guarantee the vehicle will perform as specified if other than
premium fuel is used," says Mercedes-Benz spokeswoman Michelle Murad. All
U.S. Mercedes engines specify premium.

All Porsche engines are designed for premium, too, but it's not available
everywhere. "Our cars must be able to drive all over the world, and so we
are able to run on regular," says Jakob Neusser, director of powertrain
development at Porsche's research and development center in Weissach,
Germany. "You don't have to feel that a mechanical problem or anything else
will happen" using regular gas, even in the highest-performance,
regular-production Porsches.

Premium, in fact, sometimes is worse fuel than regular. It resists knock
because it's harder to ignite than lower-octane fuels. As a result, some
engines won't start as quickly or run as smoothly on premium, notes Gibbs,
the SAE fuel expert.

High-test does have a potential fuel economy benefit. It is slightly denser
than lower-octane gas, meaning there's a little more energy in a gallon. But
the small difference is hard to measure in real-world use, and that same
density can contribute to undesirable buildup of waste products inside the
engine.

No data show that engines designed strictly for regular run better or longer
on premium.

The Federal Trade Commission, in a consumer notice, emphasizes: "(I)n 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."

There is "no way of taking advantage of premium in a regular-grade car,"
says Furey.

"There is no gain. You're wasting money," insists Jim Blenkarn, in charge of
powertrains at Nissan in the USA.

"No customer should ever be deluded into thinking there's any value in
buying a higher grade of octane than we specify," says Toyota's Paul
Williamsen, technical expert and trainer.

But premium retains a mystique.

Even Mayne, the sensible Subaru owner who has switched to regular, says
she'll buy premium when her neighborhood station has a special price. "It's
my perception that I might get better gas mileage or that it might be better
for my engine," she says.

"I would stop driving rather than use a lower grade of gasoline," says
Andrew Martschenko of Boston, who drives a 2003 Nissan Maxima. Nissan says
premium is "recommended" for that engine - automaker code for regular is OK,
but you'll only get the advertised power on premium.

If the price difference between regular and premium grew to $1, Martschenko
says, "Then I might consider trading down" to regular.

Guilt plays a part

Some people feel almost guilty, as if they are abusing their cars, when they
don't burn premium, says gasoline retailer Jay Ricker, president of Ricker
Oil of Anderson, Ind., which operates 28 stations. "They go all the way down
to 87 (octane), but maybe every fourth tank they put in the good stuff."

Sam Turner has seen the appeal, too. He's president of Favorite Markets of
Dalton, Ga., which operates 139 outlets in three states.

He recalls visiting one of his stations during a price war with a nearby
station, which had cut the price of premium to just 4 cents more than
regular, instead of the usual 20-cent difference.

"A customer was waiting and asked me if I was going to match the guy across
the street. I said, 'Yeah,' and he said, 'Good. For 4 cents, I'm gonna buy
super.' "

Basskisser wrote At the advice of an OMC tech who used to post here, I
started using
high test in my 1973 135 Evinrude, and it made a hell of a difference.
I had trouble getting the thing to idle smoothly in gear. I rebuilt
the carbs, did a link and sync, etc. The high test instantly cured my
idle problem, and ran great at wot.