The reduction of oil demand for automotive engines has been driven recently by the need to reduce oil pump capacity so that benefits from having a smaller size, including a reduction in power loss and CO₂ emissions. Crankshaft bearings are generally attributed to be the largest consumers, main bearings in particular since the supply pressure in the upper bearing shell oil groove over a large arc (circumferentially) coincides with high average clearance.Measurements of oil flow indicate that the main bearing groove is significant and there is a trade-off between lower oil flow and higher bearing temperatures. All solutions must ensure that the oil supply to the big-end bearings via crank drillings is not compromised.Numerical simulation tools can be used to predict and optimize the total oil flow required by the engine lubrication system. In this work, the Elasto-Hydrodynamics Simulation (EHL) was used to analyze the oil flow required by the crankshaft main bearings. In addition, the influence of some crankshaft and bearing feature designs such as, bearing clearances, bearing oil groove configurations and crankshaft oil drilling among others, were investigated in terms of oil flow requirements.For the tested engine, the total oil flow requirement could be reduced by 20% by reducing the size/capacity of the oil pump by this amount with plain upper main bearings, using a "1-to-2" crank drilling configuration. With the maximum flow reduction via "plain" upper main bearings, a temperature rise of 5-10°C was measured, but this did not jeopardize the performance of the big end bearings in durability tests.