I hate to say it, but I'm 100% sure that Boston Bob has it backwards.  There are probably other fuel formula differences that explain why modern gas doesn't work well in air cooled engines.

Bill

---------- Original Message ----------------------------------
From: "Mark Dorm" <mark_hb@hotmail.com>
Date: Tue, 05 Sep 2000 20:41:07 PDT

>You know what you're saying makes sense. MON = a, (M+R)/2 = b, RON = c where
>MON<RON means that a<b<c. So have I understood Boston Bob backwards or does
>he have it backwards?
>
>http://www.bostonengine.com/articles/todaysfuels.html :
>"For instance,  93(R+M)/2 method octane  "high-test " is not even sufficient
>for the  upright VW engine with a posted minimum RON octane number of 91."
>
>
>>From: wb6otg <wb6otg@INTREX.NET>
>
>> >There's a sticker beside my fuel cap than says minimum octane to put into
>> >the tank is 91.
>>
>>I think its time for the annual lesson on octane.
>>
>>Back in the dark ages (prior to the US government confusing the issue)
>>there were two ways of measuring fuel octane, motor (based on observing the
>>fuel's performance in an engine), and research (based on chemical
>>analysis).  These methods gave different numbers, with research octane
>>giving the higher number.  The US government couldn't decide which one to
>>use, so they invented a third system! (the average of the motor and
>>research numbers)
>>
>>So, if a gas pump in the US says 87 octane, its really 91 research octane,
>>the minimum for our Vanagons.
>>
>>Take a look at the sticker on the (US) gas pump next time you fill up. The
>>fine print will say (R+M)/2 method, or something like that.
>>
>>Bill
>
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