The Logan Superior Hydraulic Jar is a straight pull, up only, jarring tool that utilizes a special valve section to meter oil from one side of the piston to the other side. This allows for controlled jarring action during stuck fish recover. The straight pull load applied by the operator controls the intensity of the jarring blow. The downhole jarring blow is infinitely adjustable without any rig floor adjustments necessary prior to the run. Impact of each blow can be varied by simply changing the pull load.