Monodisperse ZrO 2 nanoparticles with a particle size of about 6-7 nm and low volatile multialkylated cyclopentanes (MACs) lubricant were prepared and characterized. The effect of ZrO 2 nanoparticles as additive on the friction and wear behavior of MACs base oil was investigated. The friction and wear performance of 2 wt% ZrO 2 nanoparticles ? MACs was evaluated using an Optimal SRV oscillating friction and wear tester, with a steel ball sliding against the same steel counterpart disc. Results indicate that the wear resistance and load-carrying capacity of MACs base oil were markedly raised and its friction coefficient changed little when 2 wt% ZrO 2 nanoparticles were added to it.