Prion diseases are only transmitted through ingesting neural tissue which was never intentionally fed to cows, it was a contaminant of the feed.

Biker Ray-
They did the experiment over the course of one mile and the car was already up to speed at the start of that mile. Meaning that the long term affects of the extra weight were not part of the results. They even stated that the extra weight of the clay would, indeed, eventually cause a negative impact on fuel efficiency and that the cost of fuel to get the car up to speed were equally negative.

However, the point of the experiment was to see if the evenly dimpled surface would have a "golf ball-like affect" and decrease the drag and fuel consumption. Since metal doesn't easily form uniform dimples, they were forced to coat the car in clay and dimple the clay. All of the experiments were carried out on the same course and at the same speed, meaning that the per mile fuel consumption can be compared and a fairly accurate conclusion can be reached.

Oh my God! How did my two-year-old break into their house! The dog is just about the only thing that my son has not tried to draw on. Luckily, his main medium is chalk (he gets it by crawling out the dog door and raiding the sidewalk chalk). All of our permanent markers are high up and out of reach (which is probably more of a dare to him than a means of keeping it out of his reach).