Date:         Mon, 21 Jul 1997 02:21:22 -0400
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         SyncroHead@AOL.COM
Subject:      Re: Octane

In a message dated 97-07-20 19:26:40 EDT, wb6otg@INTREX.NET (Bill Collins)
writes:

> 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

Motor Octane Number

> actual engine.  The two systems usually give somewhat different
> numbers.

RON is always significantly higher than MON

>Most car makers (including VW) specified research octane, often
> listed as R.O.N. (Research Octane Number?).

Yes, RON or R.O.N. is 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.

(Research + Motor) / 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.

The RON is typicall about 4 points or so higher than the (R+M)/2  number.

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

Unfortunately yes.  Also, many motorists believe that the Octane number is
somehow a measure of the "goodness" of the gas.  It is simply a measure of
the fuel's ability to resist compression detination, allowing higher
compression engines to operate with higher Octane Number fuels.  I'd guess
that 1/2 of the "premium" gas sold in the USA is put into cars where it does
has no useful function, other than make additional profit for people in the
fuel business.

Regards,
Jim Davis