Nice shots. I reckon if you want to accentuate the fog then you need to focus on something nearby with the lens quite wide open. Then in post if you shoot raw and use photoshop you can reduce the clarity slider a bit or use a large radius when sharpening and the fog will look much thicker. I achieved just such a result with this shot only it wasn't fog it was light.
Not tried it out on fog myself - so no guarantees.
Anyone experienced at shooting rain care to pass on any tips?! Tried the other day and you could barely tell it was raining in the shots, despite it being a downpour including some hail. I guess slow shutter speed and tripod would be a good start..