The mechanism of wear of marginally lubricated metal surfaces was investigated under high nominal pressure, low speed, and small amplitude reciprocating sliding. Oxygen-free high-conductivity (OFHC) copper was slid against HY100 steel, alloy 718, and OFHC copper counterfaces in an “inert” mineral oil environment. The results have shown that the mechanism of friction in steady state was plowing. The depth of deformed region in the copper bearing specimen was proportional to the coefficient of friction. Moreover, the wear was related to the friction coefficient by a fourth-power relationship.