re: Oil on concrete

Once the stain is set I've never been successful at removing it. If the stain is fairly new, you can get a commercial degreaser like Purple Power and spray all over the stain. Let it sit for awhile then pressure wash. This will lighten it. I've had some success with gasoline and also brake cleaner, but the brake cleaner can lighten the concrete compared to what's around it which sometimes just makes it look worse.

I have heard and read good things about this product: LINK . I've never had any personal experience with it though.