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Old 07-18-2003, 12:01 AM   #1
Scooby Newbie
Member#: 39187
Join Date: Jul 2003
2004 Impreza

Default Reply from chevron concerning octane

Mr. Buckley,

Thank you for your inquiry. It has been forwarded to us here at Chevron
Fuels Technical Service.

Chevron does not market a gasoline with higher than 92 octane in Idaho
or in any of the western states. There is no plan to do so in the near

There has been a reduction in the Antiknock Index (AKI) (also commonly
known as "octane" - the number posted on the dispenser pumps at the
service stations) in the Supreme (Premium) grade of Chevron gasolines.
This likely has been the case in most all other brands of premium grade
gasolines marketed in California and most of the Western states. This
reduction took effect August 1, 2001.

Chevron converted to lower octane for Supreme gasoline in response to
changing pipeline specifications in these Western states. While Chevron
was not in favor of reducing the octane of Supreme, complying with this
change allows for the continued efficient and reliable distribution of
gasoline to consumers.

As you know, your vehicle owner's manual contains information on the
octane required by your vehicle. However, make sure that the value
mentioned in your owner's manual refers to the "Antiknock Index" or
octane number. Some manuals may suggest limits on one or both of two
other numbers (the Research Octane Number (RON) and the Motor Octane
Number (MON)) that are used to calculate the AKI number rather than on
the octane number itself. The Antiknock index is defined as (RON+MON)/2
(RON + MON divided by 2). The RON is typically 97.5 for 91-92 AKI
premium gasoline. MON for premium is about 87.3.

The Antiknock indexes of gasolines offered for sale are set by gasoline
refiners and marketers based on their perception of the technical and
competitive needs in the market. Federal and many state regulations do
not control AKI values, only that the posting on the dispensers
accurately reflect the AKIs of gasolines being sold. The AKI of premium
gasoline in some states is higher than it is in others. This is the
result of competition. The AKI of all grades of gasoline are lower in
the high altitude areas of some Rocky Mountain States. This is because
the octane requirement of older engines without engine control modules
decreases with altitude. At higher altitudes, these engines perform as
well on the lower AKI gasolines as they would at sea level on higher AKI

Using a gasoline with an AKI lower than that required by your vehicle
may cause the engine to knock or, if the engine is equipped with a knock
sensor, decrease the vehicle's power and acceleration. Using a gasoline
with an AKI higher than that required by your vehicle provides no
additional benefit.

When vehicles are new, we tell our customers to be guided by their
owner's manual for octane selection. The auto manufacturers (OEMs) do
extensive testing to determine the minimum fuel octane compatibility
needed for their vehicles and make recommendations accordingly. Seldom
is the recommendation higher than 91. An older vehicle may obtain
improved operation using a higher octane gasoline than recommended in
the owner's manual, if the buildup of engine combustion chamber deposits
are causing knocking, pinging, run-on or reduced performance.

If you need to find higher octane than what Chevron has available, you
may check with our competitors; however, they probably have some of the
same numbers as Chevron.

One company that makes specialty fuels is the specialty fuel blending
operation within Chevron-Phillips Chemical Company. C-P Chem is a
separate company, operated as a joint venture between ChevronTexaco
Corp. and Phillips Petroleum. Try these two INTERNET sites:



www.p66race.com/ (for racing fuels)

Remember that most racing fuel is probably not legal for use in common
on-road driving in the United States (since it contains some lead). Lead
is no longer legal anywhere in the US for normal on-road use.

You may also want to contact your car manufacturer directly, since they
will be the best ones to advise you. A car manufacturer would ordinarily
not make a model for sale in a region where the only gasoline
appropriate for use in that model (and in that region) was unavailable.
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Old 07-18-2003, 12:21 AM   #2
Scooby Newbie
Member#: 25410
Join Date: Sep 2002
Chapter/Region: NWIC

Just one more example of "The Man" trying to keep us down!
Chumpsteak is offline  
Old 07-18-2003, 02:36 AM   #3
Scooby Specialist
Member#: 13535
Join Date: Dec 2001
Chapter/Region: SCIC
Location: Redlands, CA
2006 300C SRT8
11 Durango 03 Vette Vert

Default Yeah....

We redueced the octane rating 1 to 91, but on the bright side, you get to pay the same price.....
IEWRX is offline  

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