DG is shorthand for Dollar General Stores. Folks in the south love them because you you don't have to get as dressed up to go there as you do to go to Wal Mart.
A DG was built on the way to my home ski resort and I dearly love the place...an easy stop to buy some grocery basics for cheap and I also get cheap fleece there to use as pajamas (but certainly not for skiing, I am a wool guy for base layers now). We used to have to go to a weird little out of the way grocery or half an hour to the nearest real town.
Since when is five bucks a quart for fake synthetic of suspect quality at a dollar store a good buy?
This is all day long / 356 at Sam Walton's for Xom and BP and Royal Dutch stuff
BTW, O.P look for WPp in raised letters blow -molded on the bottom of the bottle near the split-seam.