If you are using the center lock, there is no need to add diff oil. The diff will be locked once you put the center lock in there. As for using the oven to break the loctite loose, I put the oven at 325 degrees F and the diffs were in the oven for about ten minutes. Use gloves when you are disassembling the diff!! Or if you don't want to use the oven, people have used a soldering iron and put the tip of the iron to the head of the screw to break the loctite. But I have not used the soldering iron method.