When a user signs up for Gnosis Car, a new Safe contact is created on their behalf. This Safe can only be controlled by the user through your Gnosis App wallet. Therefore, the funds in your Safe will not be held by any third party, and you will have sole control over the ownership of your funds.
The Safe will be configured with modules controlled by the user that allows the Card to spend funds on behalf of the user up to an allowance set by the user. This ensures that user custodies their funds in the way they prefer.