Which of the lubricants listed is the best to use on a reciprocating pump rod?

Correct Answer: Option B — Graphite and oil.

Graphite and oil provide a superior lubricant film for reciprocating pump rods. The graphite acts as a solid lubricant that fills microscopic surface imperfections, reducing friction and wear between the rod and the packing, while the oil carrier ensures even distribution and helps dissipate heat during the reciprocating cycle.