Abstract: An oil filtration assembly is described herein comprising a container having an upper end portion and a lower end portion, an oil reservoir formed on the lower end portion of the container, and a removable oil filter subassembly integrated with the upper end portion of the container. The subassembly comprises a filter housing including an inlet configured to receive oil and a filtered oil outlet configured to permit an outward flow of oil into the oil reservoir, a filter contained in the housing and disposed between the inlet and the filtered oil outlet, and a top component configured to be removed for replacement of the filter. The oil filtration-reservoir assembly further includes an inlet service valve, an oil outlet service valve and at times a service valve for the vent line. Corresponding systems and methods also are disclosed.