From Wikipedia (as good a source as any for this purpose -- the information below is accurate):

"Anti-Knock Index (AKI)

In most countries, including Australia and all of those in Europe, the "headline" octane rating shown on the pump is the RON, but in Canada, the United States and some other countries, like Brazil, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI, and often written on pumps as (R+M)/2). It may also sometimes be called the Pump Octane Number (PON).
Difference between RON and AKI

Because of the 8 to 10 point difference noted above, the octane rating shown in Canada and the United States is 4 to 5 points lower than the rating shown elsewhere in the world for the same fuel. See the table in the following section for a comparison."

here are the relevant data from the table:  "regular" gasoline in Australia, New Zealand, Canada and the US 	RON -- 91–92 	MON --  82–83 	AKI -- 87

RON and MON are two different values determined by different test methods.

The long and the short of it is, the label on your van is referencing RON, because that is what is on pumps in most of the world.  AKI is the mean of RON and MON, and is what is on pumps in the U.S.  

mcneely

---- Mark A Kippert <vanagon@KIPPERT.COM> wrote: 
> On Aug 22, 2012, at 12:12 PM, Scott Daniel - Turbovans wrote:
> 
> > I am strongly against premium fuel in stock vanagons.
> > If you want more octane use mid-grade.
> > if it doesn't ping, you're ok.
> 
> 
> I have to say I'm a bit confused. I run a higher octane in my '87GL because to label next to the filler says (in several languages) to use a min. octane of 91. That would be premium, at least here in Indiana.
> 
> Have I been wasting my money?
> 
> 
> Mark K
> 1986 GL/2WD/4SPD "Abe"
> 1991 GL/2WD/4SPD "Ruby" (sold)

--
David McNeely