The various AF Area modes exist for you to tell your camera where it should focus on a given subject. There are anywhere between 2 and 5 options on Micro Four Thirds cameras, but in keeping with most of the advice I have given so far on this site, it makes sense to play to the strengths of the system and keep things simple.
The obvious option to go with would be one of the tracking modes, but in my experience the camera simply cannot keep up with a fast moving object such as a car, instead, select Single Area/Point AF mode. In Single Area mode you select the focus point and the camera will attempt to focus in that area only. The great thing with Micro Four Thirds bodies is that you can place the focus point anywhere in the frame, even right in the corner or along the edges, opening up plenty of ‘interesting’ framing opportunities when tracking a fast moving vehicle.