A comparative study on lubricating oil degradation is carried out to assess the durability of a single cylinder diesel engine fuelled by biodiesel blend (20 per cent) and diesel, respectively. Initially, the engine is made to run with diesel for 256 h, each cycle comprising 16 h as per the IS 10000 standards. The same test cycle has been carried out on the engine which was later fuelled with biodiesel. Various tribological properties of lubricating oil such as kinematic viscosity, density, total base number, moisture content, ash content, pentane and benzene insoluble are recorded at regular intervals in order to correlate the effect of fuel chemistry on lubricating oil performance and engine life. Kinematic viscosity, flash point and total base number were observed to be lesser in biodiesel blend fuelled engine. Density, ash content, moisture content and insoluble were found to be higher in biodiesel engine. Wear debris concentrations in the lubricating oil samples drawn from both the engines were measured by Inductive Coupled Plasma-Atomic Emission Spectroscopy. Higher wear metal concentrations were observed in the lubricating oil of PME20 fuelled engine. Surface roughness parameters of cylinder liners were investigated and compared to quantify the cylinder wear of both engines. Ferrography tests of lubricating oils also indicated the significant deterioration of lubricating oil in biodiesel blend fuelled engine. (C) 2015 Elsevier Ltd. All rights reserved.