In this work the performance of graphene based nanolubricant using a 4-stroke IC engine test rig is investigated. A nanolubricant is formulated using graphene nanoflakes and engine oil meeting API 20W50 SN/CF and API 20W50 SJ/CF specifications. The addition of 0.01 wt% graphene to API 20W50 SN/CF results in 23% enhancement in thermal conductivity (k) at 80 degrees C, and 21% reduction in the coefficient of friction (mu). Moreover, 70% enhancement in heat transfer rate of the engine is also achieved in the presence of graphene. SEM images of the piston rings collected after 100 h of engine operation show that the oil containing graphene (12 nm) decreases. the piston wear compared to base oil without graphene. (C) 2016 Elsevier Ltd. All rights reserved.