We had a similar sort of problem here in the UK a few years ago. When leaded petrol was phased out, the oil companies supplied what they called "Lead Replacement Petrol" or LRP as it became known.
The official reason for this was to give owners of older vehicles a fuel with which to run them on; there was however a more practical reason.
Lead destroys catalyctic convertors as you all probably know, and apparently it takes a while (about six months of refilling a tank on the average gas station forecourt) to get rid of all the residual lead before they can put lead-free fuel in. So as to save hassle with warranty claims etc, the fuel companies brewed up LRP as a stop-gap.
With me so far?
Now, over here, we have a thing called British Standards, which is a system of type approval for a variety of commodities and products including gasoline and other fuels. Leaded fuel was made to a certain BS number (don't laugh that's what they're known as!
) and unleaded to another; however LRP being a stop-gap fuel was exempted. This provided an excuse for the fuel companies to shove all kinds of crap into LRP that they wouldn't get away with in the others, resulting in a lot of fuelling hassles. Most of these were blamed on the age of the vehicles concerned of course rather than the fuel!