Last night I filled up my truck with some of the new ULSD. I also added about half a bottle of Power Service (gray bottle). The pump only let me put $50 in, so I ran it twice. The second time, it put in about 5 gal and then turned off. When I was about to pull the nozzle out of the filler, my tank "burped," and sent diesel fuel out of the filler. Is this some sort of reaction between the ULSD and the power service, or could I have a problem with the vent on my tank? Also, the fuel was green. Is this a dye they're using to identify it as ULSD?