Date:         Mon, 15 Jul 2002 13:56:53 +0100
Reply-To:     Clive Smith <clive.harman-smith@NTLWORLD.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Clive Smith <clive.harman-smith@NTLWORLD.COM>
Subject:      Re: 85 octane in Colorado
Content-Type: text/plain; charset="iso-8859-1"

>If everything is up to spec, you won't see any difference between 93 and
98 octane as far as performance and mpg are concerned. Octane has nothing
to do with either of those factors. The Super Unleaded probably has other
additives that affect the performance.<

John,
Thats what I was taught at college too, except that as far as performance
goes, it does seem to be a bit perkier - maybe the Super UL 98 has a higher
benzene content and other additives as you say and the 10:1 DJ likes this.
As far as mapped ECU system with knock sensor (which the DJ isn't)  is
concerned, it could definitely make a difference as any backing off of the
ignition under load would not be as early if at all - but these are really
turbo or supercharged issues.

Clive Smith
'88 Syncro Transporter


----- Original Message -----
From: "John Brush" <jbrush@AROS.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, July 11, 2002 5:59 PM
Subject: Re: 85 octane in Colorado






> >And my aviation point was also wrong, as the aircraft have to take-off at
> >sea level!
>
> Oh yea, I didn't even think of that. Performance at take-off is probably a
> serious issue :-)
>
> >harm at high throttle openings. I also can't see that having differing
> >fuel specs all over the place is in any way a good thing, or easy to
> >administer, or even cheaper having non-standard mixes.
>
> From the POV of the octane, if it was cheaper to make it all the same, you
> can be sure the oil companies would be doing just that. It must be cheaper
> to be 'elevation sensitive' or they wouldn't put up with it.
>
> There are many other additives that differ from state to state, so maybe
> the octane isn't that big a deal to them. <shrug>
>
> >Octane ratings
> >higher than the minimum required don't actually do damage to an engine,
>
> Until I was recently proven to be wrong by a someone's technician, I had
> been taught by the gasoline companies I worked for, that lower octane is
> cheaper, so wherever it provides the same performance, it is used. Lower
> elevations require higher octane, which costs more to produce.  If the oil
> companies had their choice, the whole country would get 85 as the low end,
> but since that doesn't work, they put the 85 octane in all the places that
> it will perform correctly. Higher elevations.
>
> >The DJ needs 93 minimum at Sea level. It runs a 10.5:1 CR as standard
> >from the factory. It goes better with 98, Super Unleaded and does another
> >mpg maybe.
>
> If everything is up to spec, you won't see any difference between 93 and
> 98 octane as far as performance and mpg are concerned. Octane has nothing
> to do with either of those factors. The Super Unleaded probably has other
> additives that affect the performance.
>
> Interesting day here in Vanagonville, ain't it? :-)
>
> John