The blowjob in the car is one of those things that is awesome simply in and of itself. Slightly cooler than the blowjob in the hammock but a little less fantastic that the blowjob in the space shuttle, the car smoothie is intensified by the fact that it adds a precise element of danger to the proceedings.
As the driver of the car, I know I have to keep my focus on the road. Because, man, there's big-ass trucks and crazy seventeen year old girls trying to simultaneously text their BFFs and steer a Lincoln Navigator across six lanes of highway out there. But as the recipient of the blowjob, I also know that the lifeblood which is so necessary to keeping my brainwaves nice and snappy is being filtered away to my lower extremities, giving me that slightly dizzy, slightly buzzed, holy-shit-I'm-getting-a-beaner-in-the-car feeling that truly dulls the reaction times.
Also, if it's a particularly long drive, and said blowjob is helpful in keeping me from slipping off into a narcoleptic coma on interstate 95, then I certainly want to prolong the sensation and retain my seed for as long as possible (which for me, ladies, ain't all that long). But that increases the risk of being discovered by a fellow driver who might snap a quick vid of the proceedings and throw it up on YouTube.
Worst of all, as a guy who just hasn't mastered the art of post-orgasm smalltalk, I find myself in a precarious situation once the BJ has officially ended and I realize I've still got 65 miles to Boston. Once, after a Kennette obliged me in the car, I simply nodded, smiled, said, "Woah" and "Awesome" and then proceeded to mess with the radio buttons for the next twenty minutes.