Most "Gas Stations" will not know (attendants even less) or even think about as it is all about their cost at the pump to be competative. The haulers that come out of the terminals play a big part in what is in the underground tank below the pump. Many "gas stations" may put the sticker on the pump to be legal but in reality may not have the new ULSD. One is because you have to have either run gas in the truckers tank compartment or two, steam clean the truck tank before hauling the ULSD...I guess you could also have special trucks hauling only it too but that would be expensive to the hauling company.
At the loading terminals for the tanker trucks they also would have to have special lines that would only have ULSD to the truck. Currently, they generally have one hose they hook up to the tank truck and fill one compartment(1500 to 3000 gallon compartments) at a time. When that compartment is full they move the same hose to the next compartment and pick what fuel and amount to load into that compartment. Those choices would be different grades of gas, premium #2 diesel, regular #2 diesel, off road #2 diesel, Bio-diesel in any ratio you can think of but commonly B5, B11, B20, B50, B100, ULSD diesel, Heating oil, red or white Kerosene, and more I can't think of right now. Depending what the truck ahead of yours loaded last and what was in the tank before the current load it could have traces of anything. Push of the button and here it comes. It really depends on how alert the driver is as to the amount of contamination in the tanks. Unloading also. Usually they only haul ~8000 gallons or less total due to the weight restrictions on the truck in the 4-5 compartments. If one compartment had off-road (Red) or 500ppm diesel for example, in it before hand, the ULSD the driver just put in it is now considered compromised and can not be considered USLD, legally. If the driver just had gasoline in the tank the load before getting the ULSD it would be OK. Most places that get it and redistribute it will have to dedicate special tanks, piping and pumps for this stuff and that adds to the cost of handling it so most will not bother until 2010 when it is mandated unless specificially asked. Adding any additives to the tanks is a whole other issue also. Some do and some do not.
My take is that if you have an engine that requires the ULSD you are going to have a real hard time in the next few years finding the correct real ULSD fuel that has not been contaminated with the regular diesel or anything else.
That is my take on the ULSD issue.
(My personal opinion based on recent experience)
