Fwd: A Chemist's view on octane (Long)

From: O26ON4@aol.com
Date: Mon Sep 14 1998 - 07:41:19 EDT

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I got this off the Grand Prix mailing list, thought it would be of interest to
ya'll.
Enjoy,
Steve Waller in Houston

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Date: Sun, 13 Sep 1998 07:35:50 -0400
From: Paul Berndt <pberndt@worldnet.att.net>
To: GP Mailing List <grandprix@maiden-voyage.pagesz.net>
CC: Tom Johnson <tjohnson@FLEX.NET>
Subject: A Chemist's view on octane (Long)
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GP'rs

With all of the recent discussion on brands of gasoline and which is
best, I had this post from earlier in the year. It came from the
VetteNet but should apply to our cars as well. He makes some good points
and has the credentials to validate. I had to get Tom's permission to
repost it as you should if you pass this along.

Paul Berndt
'97 GTP Coupe

Subject: A Chemist's view on octane (Long)
   Date: Sun, 29 Mar 1998 19:50:06 -0600
   From: Tom Johnson <tjohnson@FLEX.NET>
     To: VETTES@ASUVM.INRE.ASU.EDU

Someone in the octane thread asked for a chemist's view on the subject,
so
here's mine. However, first a view necessities and background:

Credentials: Ph.D. Organic chemist, 21 years as a practicing chemist,
28
US patents (many on gasoline additives), work for a major oil company
that
is a leading (by volume) retailer of gasoline in the world. I've had
engine tests (meaning an engine on a fixed engine stand run by a
computer)
and road tests (meaning cars driven by humans -- some on a course, some
not) run on gasoline additives I've invented (while employed at the oil
company). These additives have been tested in the US, England, and
France
under a variety of conditions. Many of my additives have also been
tested
in the BMW test (10,000 miles). I'm still employed by said oil company.

Disclaimers: The views expressed here are my own and not the company I
work for (which is why I don't mention the company, although I realize
any
enterprising person could easily find out).

Copyright: This entire note is copyrighted by the author. Participants
in
this mail group may store and make one copy for their own use.
Participants may refer to, copy, send, and re-send to participants of
this
mail group and post or re-post sections of this note as long as this
copyright notice is attached. Except for these specific exceptions,
this
note may not be copied, quoted, or transmitted in any form for profit or
non-profit, or used for any type of publication without written
permission
from the author.

Corvette: Mine is a 1979 that is on its second trip through the
odometer
(and its second engine, and third interior). I've owned it
approximately
12 years, love it, and may never get rid of it.

Octane: I've seen many consumer magazines tell their readers that they
are wasting money to buy a higher octane gasoline if their car doesn't
knock. If octane were not related to any other feature of the gasoline,
I
would agree. However, how companies get higher octane gasoline does
make
it different than regular and mid-grade gasoline. So the question to me
then is, do these differences make a difference? The short answer is
what
do I use, and I use regular in all my cars and my truck. I use premium
in
my Corvette. Why? Because as any Corvette enthusiast (to separate us
from
people who merely own one -- no flames, please) knows, a Corvette is not
a
car, it's an experience. If you want to know the long answer keep
reading.

Base gasoline: Crude oil differs depending on where it's from, and
consequently, what comes out of it when it's refined also differs.
There
are books on the subject and I can't possibly do the subject justice
here.
As the oil differs, what is available for blending and cutting is
different. In the end, however, the refiner has to make economic
choices,
based on what's available to him from the oil he is refining, on how to
get
the required octane to sell (as well as meet MANY other criteria that
make
gasoline, gasoline -- again I can't do justice to it here). What I
generally (but not exclusively) see is that BASE (no additive added to
it --
you can't buy this, it isn't offered for sale) premium gasoline leaves
less
deposits behind than other grades. There are certain types of molecules
in
regular and mid-grade BASE gasolines that simply do not exist in premium
gasoline that cause much of this. Additives (see definition below) are
added to the gasoline to help get rid of these deposits, and modern
additives do a marvelous job of this. What you buy is additized
gasoline.

Blending components vs additives: MTBE (methyl tertiary butyl ether --
this is ether) and ethanol are blending components, not additives.
However, you'll see them called additives in many places by many people.
Blending components are part of base gasoline. The simplest
differentiation between an additive and a blending component is that the
former are added in ppm (parts-per-million) levels; whereas, the latter
are
added in percentage quantities.

Brand of gasoline: Some of you probably know this, others may be
shocked
by it. Oil companies swap base gasoline all the time. Let's say I have
a
refinery in Houston and you have one in Dallas. It makes little sense
for
me to truck my Houston gasoline to Dallas and for you to truck your
gasoline from Dallas to Houston when gasoline is a commodity product.
So,
I let you draw 100,000 gallons of base gasoline from my storage tank in
Houston for your Houston gas stations, and you let me draw 100,000
gallons
of base gasoline from your Dallas holding tanks for my Dallas gas
stations.
That way, we both save on shipping. Yup, Texaco gasoline may have come
from a Shell refinery and vice-versa. At a gasoline terminal you may
see
trucks from up to six different companies all loading at the SAME
terminal
(that for example may be supplied exclusively by Shell). What comes
next,
however, is what makes Texaco Texaco and Shell Shell. Additive. Each
company has its own additive and adds it to the base gasoline. So while
the base gasoline may be the same, the additive is different, and hence
the
brand of gasoline you use is different because of the additive, not the
base gasoline.

Which additive is better?: Given the above discourse, it's obvious that
we
all want the gasoline with the best additive. Unfortunately, it's not
that
simple. Additives respond differently in different base gasolines (even
of
the same grade). Also, some additives work better with gasolines used
in a
carbureted car vs one that uses fuel injection. On a practical level,
additives are going to be developed today for today's cars -- meaning
fuel
injected cars. For Corvette owners who have carbureted Vettes (like
me),
this is unfortunate. Carbureted engines leave a LOT more deposits
behind
than fuel injected cars. From a regulatory stand point, California was
the
first to call for all gasolines to pass the BMW test (port-fuel-injected
engine) in all grades of gasoline. Like all regulations, this one had
various massages put to it, but the net effect was that all oil
companies
went to work developing additives that are a LOT better today than 10
years
ago AND they are used in all grades (not just premium -- hence the
argument
to use premium to get a better additive went out the window).

Insider's trick on gasoline additives: No matter what you do or what
you
drive, this trick will help you keep down deposits inside your engine.
You
see, additives themselves will make deposits and/or create a deposit
that
is different from the one made by base gasoline alone. If you think
about
this for a moment, you'll come to realize that your engine will build
some
kind of deposit based upon what additive you are using. Yes, it will
build
at a slower rate, but it will build deposits. At some level this will
taper off (but this is maximum deposits and what Corvette owner wants
that!). So what do you do? Simple, switch to a different brand of
gasoline (this will almost assure you of getting a different additive
but
not always. Some companies buy additives from other companies, so it
could
be the same. More on this later). What this will do, is the new
additive
will look at the deposit formed from the old additive as foreign and
begin
removing it. Now after 5000 miles, you'll be rid of this deposit but
you'll have a new one from your most recent additive, so switch back and
start the process all over again. As an analogy, this is like building
an
immune response to an anti-biotic, so your doctor gives you a new one.
I
know of absolutely no additive that will work as well as switching back
and
forth between additives. On a molecular level this makes perfect sense.

So what's a Vette owner to do?:
(1) Whether you buy regular, mid-grade, or premium, use one brand for
about 5000 miles, then switch to another brand for 5000 miles. I use
Shell, then Chevron, then Exxon, then back to Shell, etc. (this is not
an
endorsement). These companies have historically had there own additive
research groups/companies, so they'll likely use their own additive and
not
something they bought from each other. It is completely possible,
however,
to use a sequence like Amoco, Shell, Texaco and still come out fine.
(Again these are not endorsements). I use three companies and 5000
miles
based on what I've observed working in the research area. 7,000 miles
and
two different brands will still do wonders. As an aside, it takes most
vehicles 7-13,000 miles to build their maximum deposit levels.
(2) If your Vette is carbureted or TBI, buy premium. These
fuel-delivery
systems build deposits rapidly and to much much higher levels than PFI
(port fuel injection) systems You need every edge you can get (if
you're
an enthusiast). If I had a PFI Vette I'd still buy premium, but must
tell
you the effect will not be like in the carbureted version.

Hope this clarifies some points.

Tom

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