Miata Mailing List: February 1994, Message #149
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   From: horma200@ccmail.iasl.ca.boeing.com
Subject: Octane Numbers
   Date: Wed, 9 Feb 1994 15:03:31 -0500


>Piet RUYSSINCK writes:
>>Well, my personal average is about 8 liters of unleaded fuel (95 octane) per
>>100 kilometers.
>>That should be around 29.4 mpg if my calculations are correct.
>
>Why such high octane?  In the US. we use 87 octane, and the highest I've seen i
>about 93 octane.  Are octane ratings higher in Europe than in the US?
>
>Tom Tkacik
>tkacik@adtaz.sps.mot.com

Assuming nobody has beaten me to it (I'm a daily digest subscriber), let me
say a few words about octane numbers.

There are two relatively widely accepted methods for rating motor fuel,
which result in the Motor Octane Number (MON) and the Research Octane Number
(RON).  The MON rating is more conservative, and yields a lower number for
the same fuel as the RON, which is the international standard used by the
auto industry.  The number quoted by Piet is 95 RON, also known as "Euro
Super", which is the middle grade of fuel available in most of northern
Europe.  Here in the U.S., our bureaucrats have chosen not to use either
of the accepted standards, but to create their own, commonly known as
"pump octane" because it is the number posted on the front of the gas pump.
It is calculated as (RON + MON)/2.  87 pump octane corresponds roughly
to 91 RON, which is the standard for unleaded regular gasoline.

            Milton Horst        horma200@ccmail.ca.boeing.com
            Seattle, WA         horma200@bcstec.ca.boeing.com

        Boeing Employees Autosports Club
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