I enjoyed the comments of Jim Davis on this subject.  Part of it is shown
below.  For an 85 Waterboxer Westy is there any advantage (or need) of
running the 89 or 91 instead of the 87?

>In California typically each terminal rack will have tanks of raw 87 octane
>and tanks of raw 91 octane gasoline.  These two are blended as they are
>delivered to each truck to create the 89 octane midgrade fuel.  Almost all
>gas stations in CA have 87, 89, and 91 octane fuels available.  These octane
>numbers use the (R+M)/2 method.

Take care...Bob Marshburn
'85 Westfalia
'80 Westfalia