aFe Pro Series Rear Diff Cover Kit Black w/ Gear Oil 86-16 Ford F-250/F-350 V8 7.3L/6.0L/6.4L/6.7LThe supplied gear oil (4 quarts) exceeds the performance requirements of API GL 5 recommended for both open and limited slip applications. This cover has an increased oil capacity over stock for better performance over a longer duration. Built in internal and external fins transfer heat from the oil to the outside air for maximum cooling. This cover incorporates a magnetic drain and deep reach fill plug to capture loose particles for maximum