Some people I know shoot up to 50 rolls of film per day and only 5 of their photos from that weekend may get printed. I average about 15 rolls of film per day, a total of about 1000 exposures per 3-day IndyCar weekend. On the track, you need the longer lenses if you want to fill your image with more car and less background. Depending on the distance between you and the cars, this will usually be at least a 200mm lens, and most of the time 300mm and longer. In pit lane, a mix of wide-angle and a medium zoom lens usually work best to cover the variety of images that can be taken there.
Some photographers always carry their entire gear around the track.
I prefer to plan my day and only bring what I will be using to reduce weight and unnecessary gear dangling off my shoulders. It is not mandatory to shoot with the sun behind you, but it helps. I sometimes shoot images with rear lighting in the early morning, but later in the day, images just look better with the sun behind you. If you haven't been at a certain facility before, use the time before and between sessions you take pictures to scout out the track. I know what I am going to get once it matters.