Don't use oil on the slide. It drains away and leaves your slide dry. Oil should only be used in places like hammers, triggers etc... Any rotating or pivoting part.

You want to use grease on any parts that slide against each other. Grease stays where you put it and parts that are under load and slide against each other you want the lubricant to stay put.

Here is an article that explains lubrication properties a whole lot better than I ever could.
http://www.grantcunningham.com/lubricants101.html