[travelin texans]

I used whatever cooking oil the DW had in the cabinet, about a 1/4 cup in each tank a couple times a year after draining & flushing, have done this for years in very rv we've owned.
Also would recommend the blue Dawn rather than the Tide pods unless you dissolved them in a bucket of hot water before putting it in the tanks to be sure they dissolved completely & not leave the pod material to gum up the valve.