a. Big Macs -- i.e. unrefined gasoline b. Filet-O-Fish -- i.e. unrefined stinky #6 c. Waste from the french fry fryers -- i.e. pyrolysis sludge that nobody can use (except CoCo The Paving Clown, maybe)
Not that you can tell much from the street, but if one knew WHERE these "tankers" were going, it would be very simple to find out what kind of liquid is inside of them.