In the perspective of fuel saving and emissions reduction, engine oil thermal management has not yet received the attention it deserves. Lubricating oil, in fact, should be the focus of a specific warmup action: the expected benefits is on friction reduction – mechanical efficiency improvement – but also on a positive interaction with the cooling fluid thermal dynamics. The lower thermal capacity of the circulating oil (with respect to the cooling fluid) and the instantaneous reduction of the viscosity due to temperature increase produces a faster engine overall efficiency benefit: this invites to focus specific actions on its thermal management in the direction of speeding up the temperature rise during a cold engine starting. Being the mechanical engine efficiency strongly influenced by the friction losses and considering the important benefits on oil viscosity due to a temperature increase, important beneficial effects should be observed on fuel consumption: unfortunately, the big oil quantity inside the oil sump delays the oil warm-up which is continuously heated during the engine passage but also remixed inside the oil sump in which a great oil quantity is present. So, during a homologation cycle for passenger cars and light duty engines, the oil temperature rise is dominated by the mass inside the oil sump: considering that the oil flow rate is limited by the limited engine speed of rotation.In this paper, a modified oil sump has been designed and tested on an Iveco F1C 3 L engine test bench in order to temporarily reduce the oil quantity from which the oil pump aspirates it. In this way, the oil is remixed with a smaller oil quantity inside the sump, speeding up its temperature rise. When the engine reached a thermal stabilized state, the capacity of the oil sump is restored to its full capacity. The temporarily volume reduction of the oil inside the sump is realized by modifying it with a metal septum that divides the capacity into two parts: a thermo-controlled opening links the two parts together when the oil reaches the design temperature.Fuel consumption and CO2 emission reduction have been demonstrated and this further positive result has been added to another positive action in order to further speed up its temperature, using exhaust heat to warm the oil. Fuel consumption benefits has been demonstrated and pollutants reduction has been also reported, produced by the modified thermal behavior of the whole engine due to the positive interactions with the cooling fluid.