The Jagg offset oil filter adapter with thermostatic oil by-pass installs between the engine and oil filter for quick and easy installation of an oil cooler. The offset design is a must for all Twin Cam and Fuel Injected Evolution Big Twin but can also be used on other Evolution Big Twin and Evolution Sportster. The oil filter adapter directs oil through the filter first for optimal flow characteristics. After filtration, the oil will by-pass the oil cooler until the engine reaches standard operating temperature. Then the thermostatic actuator will close the by-pass hole, sending hot, filtered oil to the oil cooler, and delivering cool, clean oil to the engine. The optional Anti-Rotation device will ensure that the oil filter adapter will not rotate during future oil filter removal.