Abstract: A plastic fuel tank for use in a vehicle to carry gasoline, diesel fuel and the like has an upper wall, a lower wall and side walls. In order to inhibit relative deflection of the upper and lower wall toward each other, such as may occur when vacuum pressure is introduced into the tank by typical fuel sensor systems, the tank is equipped with a resilient columnar member extending between the upper and lower walls. The resilient columnar member thus limits deflection and changes in volume of the tank to not greater than one liter. The columnar member is hollow so as to not reduce the fuel capacity of the tank. The columnar member may be held in position by structural walls within the tank or by welding to either the top or bottom wall of the tank.