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, could 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. 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 have to produce a faster engine overall efficiency benefit: this invites to focus specific actions on its thermal management. Important beneficial effects have been observed on fuel consumption with a hotter oil, but limited by its great quantity in the sump which delays the oil warm-up. A so high oil quantity is needed by oil life-time but it represents a strong thermal inertia. In this paper, a modified oil sump has been designed and tested on an Iveco F1C 3 L engine test bench in order temporarily reduce the oil quantity from which the oil pump aspirates it. In this way, the oil (eventually heated by the exhaust gases) 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 f the oil sump is restored to the design value. 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 this is needed. Fuel consumption and CO2 emission reduction have been demonstrated and this result has been added to the previous, refining the oil thermal management technology and defining a benchmarking. Also a pollutants reduction has been reported produced by the modified thermal behavior the overall engine due also to the positive interactions with the cooling fluid.