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From: jparnas@vger.UUCP (John M. Sully)
Newsgroups: net.auto.tech
Subject: Re: 98 octane gasoline
Message-ID: <355@vger.UUCP>
Date: Sat, 1-Mar-86 16:50:55 EST
Article-I.D.: vger.355
Posted: Sat Mar  1 16:50:55 1986
Date-Received: Sun, 2-Mar-86 19:16:34 EST
References: <2095@dutoit.UUCP>
Organization: UC Santa Cruz, CIS Dept.
Lines: 36
Summary: regular leaded + super unleaded = higher octane

In article <2095@dutoit.UUCP>, ssp@dutoit.UUCP writes:
> 
> Does anyone know where I can obtain 98 octane LEADED gasoline?
> 
> Three "solutions" have been suggested to me:-
> 1) Mix regular leaded and super unleaded in egual proportions.
> 2) Use octane boosters.
> 3) Use racing (114 octane) fuel!
> 
> Any suggestions as to which is the best &/or the most cost-effective solution?
> 
I forget the chemical reasons for it, but mixing regular leaded and
super unleaded will actually produce an "octane hump" of 1 or 2 points.
this will result in a mix with a pump octane rating of about 93. 

Note that the octane ratings which you see posted on pumps are pump 
octane ratings.  There are two different methods of measuring octane,
the research method (RON) and the motor method.  The numbers given by
the research method are typically 5-10 points higher than those given
by the motor method and so the feds came up with pump octane, which is
simply MON + RON / 2.  So a 93 pump octane fuel should be good enough
for your motor since it calls for 98 RON gasoline.  If your engine knocks
under these conditions then the octane is too low and you will have
three choices:

     1. Use an octane booster -- expensive for a good one
     2. Use racing or aircraft fuel -- also very expensive
     3. Lower the compression ratio of your engine by installing
	a thicker head gasket. ( done on motorcycles usually )

=============================

John M. Sully
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