In a message dated 97-07-22 13:23:51 EDT, JWALKER@UA1VM.UA.EDU (Joel Walker)
writes:

> and, for example, in my local Alabama area, there are THREE suppliers or
>  distributors of petroleum products (oils, gasolines, grease, etc) from
>  ALL the petroleum companies in this country. so Friday Oil Co. (one of
>  the locals) will come out and fill up the Shell Oil station, but they
>  also fill up the Exxon station and the Texaco station. Wyatt Oil Co.
>  fills up Amoco, BP and Unocal. Hunt Oil fills up Parade, RaceTrack and
>  some other minor brands. but they all swap every now and then. it's not
>  uncommon at all to see a Shell truck at the Unocal station.

I am quite familiar with gasoline terminal rack (where the tank trucks fill
their tanks) blending systems.  I and the company I work for have provided
computer control systems that do the gasoline blending and additive
injection.

The companies I'm familar with here in California (Texaco, Shell, Chevron to
name some) are very careful blend their fuels to produce the exact octane
number that's displayed on the pump.  The gasoline gets randomly analyzed
here in CA so they have some incentive to blend to the proper spec.  I don't
know how it's done in Alabama though.  Too little octane they get fined, too
much and their throwing their money away.

While a Shell truck might fill the tanks at a Unocal station, they're still
using "Unocal" gas (at least in CA) because they'll use Unocal's additive
package.  We've had to create quite elaborate additive injection systems to
make sure that all the different fuel brands get their own additive package
in their load of gas.  Sometimes there are up to 8 or 10 different additive
sets maintained at a terminal.  Texaco trucks get the Texaco additive, Shell
trucks get the Shell additive and so on.  They typically have a generic
additive (usually made by Chevron) to add to the independent station's loads.
 Also, the "generic" Chevron additive for the indepependents is clearly
different than the additive used for Chevron's own fuel.  All the fuels from
a single terminal do have the base gasoline stock in common though.

In California typically each terminal rack will have tanks of raw 87 octane
and tanks of raw 91 octane gasoline.  These two are blended as they are
delivered to each truck to create the 89 octane midgrade fuel.  Almost all
gas stations in CA have 87, 89, and 91 octane fuels available.  These octane
numbers use the (R+M)/2 method.

Regards,
Jim Davis
87 GL Syncro
88 GL Wolfsburg