The tribological behaviour of pyrolysis bio-oil with a synthesized nano-Lanthanum oxide (La2O3) additive was evaluated using a point contact four ball tribometer under different frictional conditions. Results were compared against a micro (mu)-La2O3 additive and an un-additised bio-oil as a control. The results show that nano-La2O3 impregnated bio-oil had better tribological properties than the control groups. Under the operating loads, the optimum nanoparticle concentration within the bio-oil was investigated. At these levels, the combined action of adsorbed bio-oil films on the worn surfaces and the bearing effects of the nano-La2O3 minimized friction and wear. The tribo-mechanisms were ascribed to adhesive wear as a result of lubrication starvation under high loads, and abrasive wear at high rotational speeds as a result of combined deformation and aggregation of the nano-La2O3 particles. (C) 2015 The Authors. Published by Elsevier Ltd.