well...an oil stone, can be used dry too.
The fact is that some of the guys who have writen books about getting things sharp have talked about not useing oil ever....
One the other hand, most all the other books talk about useing oil all the time.
So although I make knives and guys at work are always asking me to sharpen their knives, I yet dont know what the correct answer is.
What i do know is that once you start to add oil to a stone, you more-or-less have to keep adding oil all the time then.
For me?, I use oil,,,lots of oil....I like my stones clean and so i really dump the oil on...Im not sure thats correct but it's what i do.
as far as i know, most sharpening stones that are sold to us guys are sold as oil stones...