It's time to change the oil in the rear end of my 2012 F-150 work truck that I recently bought. Its currently sitting at 156, 530 miles and I'm not sure if the previous owner ever changed it. its a 2wd with the 3.7 V6. I,m trying to figure out if its limited slip or not, giving the local dealer my VIN was no help. Anyway, Im considering running Redline 75W140 and changing it every 50-100k miles. I picked up a 4 oz bottle of the Motorcraft XL-3 friction modifier, in the event that it is limited slip, I'll have it when I'm ready to change it. Asssuming that the Redline already has the LS additive in it, will it hurt to add the XL-3? I plan on scraping off the factory silicone and using a Lube Locker gasket. It has a 10 bolt cover, would anyone know the torque spec? Would it be better to buy a gallon of Redline off Ebay or Amazon?