Re:fuels and octane ratings..

[Alex Kowalski (audial@aol.com) (Law Guest Account) <lawguest@wppost.depaul.edu>]

I had a few minutes to spare, so here's some data from my recently
acquired Bosch Automotive Handbook  I love this thing! :-) 

     RON, MON:
  
    The number determined in testing using the Research Method is the
Research Octane Number, or RON.  It serves as the essential index of
acceleration knock.  

     The Motor Octane Numer, or MON, is derived from testing according to
the Motor Method.  The MON basically provides an indication of the
tendency to knock at high-speeds.  

     The Motor Method differs from the Research Method by using
preheated mixtures, higher engine speeds, and variable ignition timing,
thereby placing more stringent thermal demands on the fuel under
examination.  MON figures are lower than those for RON.

    Octane numbers up to 100 indicate the volumetric content in percent of
the C8H18 iso-octane (trimethyl pentane) contained in a mixture with
C7H16 n-heptane at the point where the mixture's knock resistance in a
test engine is identical to that of the fuel being tested.  Iso-octane, which
is extremely knock-resistant, is assigned the octane number 100 (100
RON and MON), while n-heptane, with low resistance to pre-ignition, is
assigned the number 0.

...

Then it goes on to list the standards for Germany (European Standard
EN228)...

Premium :              RON 95, MON 85
Regular, min:         RON 91, MON 82.5
Super Plus, min:    RON 98, MON 88 

The U.S. uses the (RON+MON)/2 method of labeling the octane of our
pump gas, so the Super Plus 98 RON fuel should be equivalent to our 93
Premium.