The only place I have found Biodiesel in Phoenix, AZ is a store called Western States Petroleum. Anyone have an opinion on the quality of their fuel?

Have you seen their operation or talked to anyone? Do they sell blends or simply B100 and the customer does the mixing? I'm also in Phoenix and wonder if they sell it by the tank, in drums or what. Where is it? I seem to recal SW Phoenix.
How DOES one evaluate the quality of the fuel? Feed it to your car and see if it chokes? I've heard of having it tested, but have no clue where to take it, what it costs, or how to interpret the test results once I get them.

There is an Arizona forum here:

http://forums.biodieselnow.com/default.asp

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http://www.pdxbiodiesel.org

Check out westernstatespetroleum.com According to their site they have B99 and you can get it in bulk if you choose. They also state that their biodiesel is 100% soy bio.