If you can't find using address given bellow try
http://www.geocities.com/TimesSquare/Alley/7026/octane1.html
and at the bottom of the page go to: Octane explanation link.
Regards
John

> 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.