Abstract: An oil system includes a de-aerator and an oil tank. The de-aerator includes a fluid inlet, a first outlet and a second outlet, the first and second outlets both feeding into the oil tank. The oil tank includes an air outlet and an oil outlet. The de-aerator is arranged in use to at least partially separate an air oil stream entering via the fluid inlet into a de-aerator air flow including air and a de-aerator oil flow comprising oil. The de-aerator air flow enters the oil tank via the first outlet and the de-aerator oil flow enters the oil tank via the second outlet. The oil tank is arranged such that an oil tank air flow including air exits the oil tank via the air outlet and an oil tank oil flow including oil exits the oil tank via the oil outlet.