it's not even mud really, it's water on my road flowing from one puddle to another. it carries a bit of silt from the road and when it flows into the more settled water of a puddle the silty water and clear water mixed like this until the silt settles to the bottom of the puddle. im sure you've seen the effect before. and yes i've seen the oil drops i'm sitting around the house for the next week or so with nothing to do, so i may have to try a setup like that at somepoint.