Please note the deliberate mistake in my original e-mail, MON is also rated
on a single cylinder engine.
For an indepth explanation please refer to HTTP://www.osbornauto/octane.htm
The following still holds true: USA 91 has a higher RON value than 91RON as
used in New Zealand and Europe.

Regards
John.

> My understanding of the subject is as follows.
> USA 91 has a higher RON value than 91RON as used in New Zealand and
Europe.
> This is because US method is MON plus RON divided by 2.
> Since the  MON rating for the same fuel is s always lower than the RON
> rating, the result from dividing MON and RON by two will always give a
> result lower than the straight RON number.
> RON = research Octane Number, measured in the lab using a single cylinder
> engine at constant RPM.
> MON is motor octane rating, single cylinder engine tested under more
severe conditions.
> Regards
> John.
> (PS. If I am wrong please feel free to educate me!)
> ----- Or
> iginal Message -----
>
> > > MArk, I believe that our octane is actually has more "Umph".  I
believe
> > > that the average method lessens the rating.
> > > Anyone out there who can clarify?
> > SNIP SNIP SNIP SNIP
> >
> > The European method, or the German method at least, uses the RON octane
> > rating.  We, Yankees with big nukes, use a different method of
calculating
> > octane and the name escapes me at the moment.  91 RON octane is about 87
> of
> > ours.  If I am wrong I'm sure someone will correct me.  It never fails.
I
> > still have the nukes, so watch out.
>