A recent post asked if people were running the recommended octane rating
of gas in their Vanagons, and if not, could that be the cause of some of
the head problems.  This seemed a bit strange, since there is usually no
harm in using a higher octane gas than recommended, and most VWs are set
up to run on regular.  Then it hit me: the way VW specifies octane is
confusing (at least in the US).

Here's the story on octane:  At one time (up til the early '70s?), there
were two ways to measure octane, research octane (based on lab work with
the fuel) and another system (I forget the name) based on tests in an
actual engine.  The two systems usually give somewhat different
numbers.  Most car makers (including VW) specified research octane, often
listed as R.O.N. (Research Octane Number?).  The US government, in its
usual wisdom, decided that since people couldn't agree on a method, they
should invent a third one!  So, when the government started requiring
that octane be marked on the gas pump, it was required that the two
existing methods be averaged to come up with a number (the fine print on
the sticker even reads (R+M)/2.

So, when VW calls out 91 R.O.N., as the gas flap sticker on my Jetta and
the owner's manual for my Vanagon both do, that is the same (more or
less) as the US gas pump number of 87, which is the usual number for
regular in most areas.

Are people really putting premimum gas in Vanagons for this reason?

Bill