Q: What does a trunk spoiler do on a Model Y Juniper?

At the rear of the Model Y, air coming over the roof and glass meets the decklid in a high-pressure zone and can peel away, which adds drag. This spoiler extends the rear profile to create a subtle long-tail effect, delaying that separation and gently raising pressure over the decklid so the air leaves more cleanly. The payoff is a calmer wake, lower drag, and a car that feels more composed during lane changes and long sweepers.