Tribological properties of lubricating oil-based nanofluids with metal/carbon nanoparticles.

: Oil-based nanofluids were prepared by dispersing several metal and/or carbon nanoparticles in lubricating oil, and their tribological properties were investigated using a four-ball tribotester and an FZG machine. Each nanofluid can possess excellent wear resistance or extreme pressure capacity, but not both. Therefore, a new concept of mixed nanofluids was developed to satisfy both properties at the same time. The mixed nanofluids containing graphite and Ag nanoparticles not only showed enhanced load-carrying and anti-wear properties in the FZG gear rig test but also reduced the electric-power consumption by more than 3% compared to the base oil.