I specified the octane tags as "unknown" as a convenience to the next mapper, who can then more easily set them to "yes" or "no" without having to do a bunch of typing.

The initial source of the data is the state's Department of Environmental Quality which has a list of gas storage tanks with geo coordinates.  However, it's not the only source; I cross checked each station against satellite imagery, street imagery and in this case, Chevron's web site.  So it's not a simple import that can be attributed cleanly to one source.