A variable displacement oil pump is described. The oil pump has a pump body connected to an intake channel and to a delivery channel, a rotor capable of rotating inside the pump body about a rotation axis and provided with a plurality of vanes. The oil pump has an oscillating stator arranged in an eccentric position around the rotor and pivoted inside the pump body at a rotation pin. The oil pump has adjustment means for adjusting the displacement of the oil pump which acts on the oscillating stator to displace it with respect to the rotor and position it in at least one predetermined operative position. The adjustment means has first thrusting means configured to exert a first thrusting action on a first outer surface portion of the oscillating stator arranged on a substantially opposite side with respect to the rotation pin taking as a reference the rotor.