The present disclosure provides a grease composition with improved water resistance and mechanical stability at high-temperatures, including: at least one base oil; a water insoluble thickener; and a low molecular weight thixotropic polyamide composition having molecular weight distribution characteristics meeting the requirement described by the relationship: ( A + D ) ( B + C ) ≥ 0.05 where A=the % mass of the polyamide composition with a molecular weight greater than 1700 AMU; B=the % mass of the polyamide composition with a molecular weight between 1100 AMU and 1300 AMU; C=the % mass of the polyamide composition with a molecular weight between 700 AMU and 1000 AMU; and D=the % mass of the polyamide composition with a molecular weight of 600 AMU or lower (determined by GPC). The grease composition of the present disclosure provides a less than 50 penetration point change as determined by ASTM-D7342, a less than 10 mg weight loss as determined by ASTM-D4170, or both.