This article explains how the winner is determined.

The object of Yahoo! Sports Fantasy Auto Racing is to manage your team to earn more fantasy points than any other owner's team.

The better your drivers perform in real-life races, the more fantasy points they earn for your team.

Since you can change active drivers between qualifying and the start of the race, the challenge is not only to pick the best team race in and race out, but also to manage your team in a way that produces the highest possible fantasy score.