From: utzoo!decvax!ucbvax!CAD:tektronix!zehntel!zinfandel!berry
Newsgroups: net.cycle
Title: Re: Re: leaded vs unleaded gasoline - (nf)
Article-I.D.: zehntel.751
Posted: Mon Feb 14 13:18:03 1983
Received: Mon Feb 21 06:42:59 1983

#R:tekmdp:-176800:zinfandel:4600002:000:1102
zinfandel!berry    Feb 14 09:38:00 1983

True, octane is a saturated 8-carbon hydrocarbon, but the 'octane rating'
determines whether a given blenfd of gasoline is 'premium' or not.  The
'octane rating' is NOT the ratio of octane to heptane or any perversion of
this number.  The 'octane rating' displayed on gas pumps is the average
of the 'Research method octane number' and the 'motor method octane
number'.  In the research method chemical wizards perform arcane rites of
analysis on a sample of the gas and come up with a magic number indexed to
'iso-octane's' magic number (usually 100).  (iso-octane is the isomer of
octane with all 8 carbon atoms in a (more or less) straght line).  The
motor method consists of running the gasoline sample into an ANSI standard
1-cylinder Otto-cycle engine (Really!) and fiddling with the operating 
parameters (compression, spark, mixture etc.) until it starts knocking. 
An 'octane number' is derived from these parameters.  Research numbers tend
to be several points lower than motor numbers, hence the average.
	Berry Kercheval
	Zehntel Inc.
	(decvax!sytek!zehntel!zinfandel!berry)
	(415)932-6900