Northeastern University researchers tested 21 vehicles from 19 brands and found that 19 of them sent data to outside companies, often without drivers ever knowing it happened.
Vehicle telemetry, which is the stream of data a car sends about its own systems and surroundings, differs from what the paired smartphone app collects.
Researchers also noted that most drivers never read the terms they accept when setting up a vehicle app.
Amazon, Google, Meta, Microsoft, Pinterest, Snap and Yahoo all appeared among the top recipients of driver data across the tested vehicles and apps.
Where personal data ends up after it leaves the vehicle is a separate question.