I can't believe I'm getting into a pissing match over gasoline. Fine...here
is report from the API (American Petroleum Institute). Sorry I over
generalized....for new cars buy the octane your owners manual recommends
(which for many is regular), for older cars go on the grade that keeps your
car from knocking.
A Consumer's Guide:
Gasoline Octane for Cars
from Gasoline Questions & Answers for Your Car
API Publication 1580, Sixth edition, January 1996
Q. What is octane?
A. Octane is a measure of a gasoline's ability to resist knock or
pinging noise from an engine. In older vehicles, knock may be accompanied by
engine run-on, or dieseling. Knock is the sharp, metallic-sounding engine
noise that results from uncontrolled combustion. Severe knocking over an
extended time may damage pistons and other engine parts. If you can hear
knocking, you should have your engine checked to make sure it is calibrated
correctly and does not have a mechanical or electrical problem, or use a
higher octane gasoline.
In most vehicles no benefit is gained from using gasoline that has a
higher octane number than is needed to prevent knock. However, in some
vehicles equipped with a knock sensor (an electronic device installed in
many modern engines that allows the engine management system to detect and
reduce knock), a higher octane gasoline may improve performance slightly.
Q. What determines my car's octane requirements?
A. Your car's octane requirements are mainly determined by its basic
design. In addition, variations in engines due to manufacturing tolerances
can cause cars of the same model to require a different octane of several
numbers. Also, as a new car is driven, its octane requirement can increase
because of the buildup of combustion chamber deposits. This continues until
a stable level is reached, typically after about 15,000 miles. The
stabilized octane requirement may be 3-6 numbers higher than when the car
was new. Premium or midgrade fuel may be advisable to prevent knock.
Other factors also influence your car's knocking characteristics:
Temperature - Generally, the hotter the ambient air and engine
coolant, the greater the octane requirement.
Altitude - The higher the altitude above sea level, the lower the
octane requirement. Modern computer-controlled engines adjust spark timing
and air-fuel ratio to compensate for changes in barometric pressure, and
thus the effect of altitude on octane requirement is smaller in these
vehicles.
Humidity - The drier the air, the greater the octane requirement.
The recommendations that vehicle manufacturers give are for normal- to
low-humidity levels.
Your engine's spark timing - The octane requirement increases as the
spark timing is advanced. Both the basic setting of the spark timing and the
operation of the automatic spark advance mechanisms are important in
controlling knock. In some computer controlled engines, the spark timing can
only be changed by replacing modules in the computer. If they are equipped
with knock sensors, these computer controlled engines have the ability to
retard the ignition temporarily when a sensor detects knock. This
temporarily reduces the octane requirement and may also temporarily reduce
vehicle performance.
Method of driving - Rapid acceleration and heavy loading, such as
pulling a trailer or climbing a hill, may result in a greater octane
requirement. Stop-and-go driving and excessive idling can increase octane
requirements by causing the buildup of combustion chamber deposits.
Malfunctions of emission control systems - An improperly functioning
emissions control system can affect the octane requirement by changing the
air-fuel mixture or by not providing dilution gases through the exhaust gas
recirculation (EGR) system. If a malfunction occurs, your vehicle should be
taken to a qualified vehicle service mechanic. Some problems are indicated
by warning lights on the driver's instrument panel.
Q. How many grades of gasoline are available?
A. Most places that sell gasoline offer three octane grades of
unleaded gasoline--regular at 87 (R+M)/2, midgrade at 89 (R+M)/2, and
premium at 93 (R+M)/2. In high-altitude areas such as the Rocky Mountain
Region of the U.S., the (R+M)/2 number may be lower by one or two numbers.
After January 1, 1996, no leaded gasoline may be sold for highway use.
Q. Which octane grade should I use in my car?
A. Use the recommendation in your car owner's manual as a starting
point for selecting the proper gasoline. If you notice engine knock over an
extended time and your engine is adjusted correctly, try a higher octane
gasoline. Also, higher octane may provide a performance benefit (better
acceleration) in cars equipped with knock sensors. Many late model and
high-performance (turbo-charged and supercharged) cars fall into this
category.
The following documents are also available:
* News Release <http://www.api.org/pasp/_backup/octane.html> on
Gasoline Octane Study
* Octane Requirements of the Motor Vehicle Fleet and Gasoline Grade
Sales <http://www.api.org/pasp/_backup/rs083.htm>, a study by the American
Petroleum Institute [in PDF*]
* Octane Sales Match Vehicle Fleet's Needs
<http://www.api.org/pasp/_backup/octoped_copy(1).html>, an op-ed by Rayola
S. Dougher and Thomas F. Hogarty
Click here to order <http://www.api.org/cat/order.htm> API
Publication 1580, Sixth edition, Gasoline Questions & Answers for Your Car.
> -----Original Message-----
> From: Susan Hensley [SMTP:susan@bearcom.com]
> Sent: Thursday, January 28, 1999 9:14 AM
> To: Spitfire List
> Subject: Petrol, continued...
>
> Hi all!
>
> Here is a message from my busy sister, who is a gasoline chemical
> engineer with Amoco in Chicago:
>
> "The refinery ChE is about 50% right. Seems to NOT be from
> midwest/northwest. He's 100% WRONG re "minimum octane to keep your
> car from knocking" if you are talking about any newer cars, tho in
> general correct if you are only talking re Spitfires, or older cars
> without the vastly improved computer chip controls that became
> prevalent mid- to late-80's. I'll explain better when I have more
> time, maybe not 'til next week, tho."
>
> I'll send her extended response if and when I get it.
>
> Keep Triumphing,
> Susan Hensley :)
>
>
> Subject: [Fwd: petrol]
> Author: susan (susan@bearcom.com) at unix,mime
> Date: 1/28/99 9:13 AM
>
>
> Hi!
>
> Is this correct?
>
> (Nice to have an Amoco Chem E in the family!)
>
> How are you??? I hope everything is going fine!!
>
> Susan :)
>
>
>
>
> > Thats as close as you can get, the air bubble is mixed heavily with
> > kerosene,
> > used as a flusing agent between the different manufacturers products,
> > octane
> > boosters added at the storage facitity. I had a very good run around
> buddy
> > that flew the pipe line from N. Va. to Tenn. everyday in his piper, made
> > one
> > heck of a good living just looking for a color change in the earth for
> any
> > possible leaks. When the fuel arrives at the terminals, no one knows for
> > sure
> > how much is Tex., exxon and so on, they just add the booster and keep
> > going,
> > the kerosene inferior is sold off to these off-brand indepents for very
> > cheap
> > prices. Good go Joe, you did remember and I thought this would get some
> > conversation going then the first reply blew my ego right out the door.
> > "FT"
> >
> > Joe Curry wrote:
> >
> > > Fred,
> > > Lets see if I can remember....
> > >
> > > The gasoline is pumped down a common pipeline from the refinery.
> > It is
> > > pumped in batches that are separated by an air bubble between
> > them.
> > > (Not sure of the dynamics of that process)
> > >
> > > The grades are more likely a result of additives which are mixed
> > after
> > > the fuel is received.
> > >
> > > The different grades are then shipped in tank trucks to the station
> > and
> > > into the holding tanks where they are distributed to the consumers
> > > through the pumps.
> > >
> > > Am I close? Or is it all done with smoke and mirrors?
> > >
> > > Joe
> > >
> > > fred thomas wrote:
> > > >
> > > > anybody have any idea how petrol gets from the refinery to your
> > local
> > > > station, and then do they get the three different varieties, to your
> > car
> > > > ??
> > > > How is reg., hi-test & premium manufactured, lets try this on for
> > a few
> > > > days, should be interesting.
> > >
> > > --
> > > "If you can't excel with talent, triumph with effort."
> > > -- Dave Weinbaum in National Enquirer
> >
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