My experience has been to use plenty of assembly lube then just use what ever oil you will be using on a regular basis. I know for some high dollar, tight clearance engines, they do use brake in oil, but I never have. I tend to just use 15W40 and change it often. After assembly, I would change it after about 500 miles then regular changes. If you don't drive it a lot, then change it on a calander basis.
