Yes, it is possible to add more than one vehicle to your EEVEE-account!
A second (or third, ...) car can be added by going to
Settings
Connected Cars
Tap the Plus-sign.
You will be presented with the "Connect your car" screen which shows all compatible car brands. Tap the one you want to connect and follow the on-screen instructions.
If your car has been added successfully you can switch between cars by going to the Settings and at the top of the screen you will your currently selected vehicle and be able to switch between your linked vehicles.