In this work, alumina nanoclusters have been synthesized by a "wet chemistry" approach directly in a regenerated oil. The produced alumina nanoclusters have a quasi-spherical shape with diameter size < 20 nm. A systematic study of their stability in regenerated Group I lubricant oil, with and without low amounts of viscosity modifiers, was performed. Tribological tests, at an optimum concentration of 0.1 wt. %, showed a significant reduction of friction coefficient and wear scar diameter up to 21 % and 11 % with the addition of polyisobutylene as viscosity modifier.