Saving cars
Tap the heart on any listing. Without an account the list lives in your browser; with an account it follows you across devices and feeds price-drop alerts.
The heart on a card or listing page saves the car. The counter in the header shows how many you have, and the Saved page lists them.
Without an account
Your saved list is kept in the browser you are using (local storage). It never leaves your device until you open the Saved page, where the ids are sent once to fetch the current cards and are not logged. Clear site data or switch browsers and the list is gone, so if you care about it, sign in.
With an account
Saves go to your account and show up on any device you sign in on. The first time you sign in, anything saved in that browser is merged into the account. Each saved car remembers the price when you saved it, so the account page can tell you how much it has moved, and price drops on saved cars go into your alert digest.
When a saved car sells
A saved listing that disappears from the dealer is retired within about three days. It stays in your list, dimmed and marked, until you remove it, so you can see what got away.