The use of naphthenic base stocks in the formulation of engine oils has always been restricted due to certain physico-chemical properties (i.e. low oxidation stability, high volatility, great variation of the viscosity with the temperature) as well as the limited availability of this type of base oil in many parts of the world.However, modern additive technologies have permitted the formulation of high quality engine lubricants that incorporate a considerable proportion of naphthenic base stocks.This paper summarizes the experimental results followed in the development of a crank-case engine oil formulation SAE 40. API SF/CC with maximun usage of a naphthenic base stock MVIN-170 combined with HVI stocks and conventional additive technologies. The physico-chemical characterization of the MVIN-170 base stock, a conventional processed naphthenic oil that Maraven (affiliate of PDVSA) commercializes from Isla Refinery of Curasao, is presented and compared with other naphthenic oils coming from other crude sources or processes and with paraffinic base stocks of equivalent viscosity. Further, it describes the different approaches in terms of base stocks balance and additives treat rates, used in the development of the final oil formulation showing in each case the corresponding engine test results.These types of formulations appear as an excellent alternative in terms of cost/performance for gasoline and diesel engines operating in mild weather regions of the world.