An oil tank assembly for a gas turbine engine may include an oil tank having an upper compartment and a lower compartment. A baffle may separate the upper compartment of the oil tank from the lower compartment of the oil tank. A de-aerator may be included, where the de-aerator includes an oil inlet, a de-aerator outlet, and an air vent. The de-aerator may be configured to separate air from oil in an air-oil mixture such that the oil flows through the de-aerator outlet and such that the air flow through the vent. Further, the de-aerator may include a fill port for receiving oil.