This book is design to provide the understanding about nanolubricants and its usages in engine and gear. Innovations in science and technology demands more energy and hence required its efficient utilization. The lubricants used in various mechanical systems control the friction and wear as well as minimize heat generation in between contacting surfaces and thus save energy. The dispersion of nanoparticles in base lubricants for improvement of their rheological and thermal behaviour is an emerging trend since 1995. This work is devoted towards the analysis of nanoparticle effect on performance of base lubricants. The objective of this work may be enlisted as following: measure the thermophysical properties of nanolubricants; develop a mathematical model for thermal conductivity as well as convective heat transfer of nanolubricant with different volume fraction; friction-wear test for nanolubricants; CFD simulation of gear oil (SAE EP90) nanolubricant & performance test of 4-stroke diesel engine by using engine oil (SAE 15W40) nanolubricant. The work helps reader to familiar with experimental, mathematical and numerical approaches for analysis of nanolubricant.