A retail dealer who annually sells directly to the public more than 500 gallons of oil in containers for use off-premises shall post in a prominent place a sign provided by the commission:
(1) informing the public that improper disposal of used oil is prohibited by law;
(2) containing instructions for disposal of used oil filters; and
(3) prominently displaying the toll-free telephone number of the state used oil information center established under Section 371.021.