Hi Matt,

That is it exactly!!  The US uses (R+M)/2 and Europe uses the R number.
Thanks for ther reminder, but as soon as I read your post, the "neuron"
fired!

So you can't go by the high actane and directly cross reference what you
need for a DJ engine.

If the DJ engine was set up like it was in Europe, then you would probably
need 95 octane, but here in the US, the way I have it set up, 91 seems to be
fine.

Kim
Tristar #7
----- Original Message -----
From: "Matt Roberds" <mattroberds@cox.net>
To: "Vanagon Mailing List" <vanagon@gerry.vanagon.com>
Cc: "Kim Springer" <kimspringer@RCN.COM>
Sent: Monday, September 03, 2007 3:42 PM
Subject: Re: 1990 2.1L Digijet European Caravelle wiring diagrams

> > From:    Kim Springer <kimspringer@RCN.COM>
> > Date:    Mon, 3 Sep 2007 11:51:17 -0700
> >
> > I belive that the Europen octane ratings are different that those used
> > in the US, (meaning the numbers don't compare exactly), but I'd have to
> > research this again to see if it is still true.
>
> I'm pretty sure this is true.  Digging up a couple of my old Usenet
> posts...
>
> Octane ratings are determined in the lab on a test engine, and there are
> two slightly different test setups.  This produces "Research" and "Motor"
> octane numbers, with the Research number being larger.  The octane rating
> of gasoline in the US is the average of these two numbers.  I know in
> Germany they like to quote just the Research number, and I suspect the
> UK is similar.  IIRC, 87 octane (R+M)/2 is something like 91 Research
> and 83 Motor.  If I'm making the right assumption about UK octane ratings,
> your standard 95 octane corresponds to our premium 91 octane.
>
> When researching this once, I found a report
> ( http://www.api.org/pasp/rs083.pdf ) with the statement that "Octane
> numbers at the end of 1968 averaged 90.4 for leaded regular and 96.2 for
> leaded premium."  These are probably (R+M)/2, and going by the average
> R-M spread of 10 on modern gasolines, probably correspond to around 95.4
> Research and 101.2 Research.
>
> Flipping through the back of the Bosch Automotive Handbook, 5th edition,
> it seems like in 1996, most "ordinary" cars used something like 9.5:1-
> 10.5:1 on 95 Research gasoline.  Of course, the gas itself is fairly
> different, and many of them have knock sensors to back off the timing
> when the engine starts to pin(k|g).
>
> For far more than you ever wanted to know about it, see
> http://www.faqs.org/faqs/autos/gasoline-faq/part3/ .
>
> Matt Roberds
>