The DeWalt SDS rotary hammer is light years better than any cordless rotary hammer I've used. Drilling holes in concrete, stone or masonry takes only a few seconds. However, using it to break concrete can be too much. I was moving the shower drain in our bathroom and noticed the grease on the piece but when I pulled it out. I could be wrong, but after a little digging I found that the grease shouldn't flow out of the cartridge. This could be a sign that it has overheated and broken the sealβ¦