At minimum? Zero. The first logician was driven to the bar by his friend, who then biked home, leaving the car in a local garage. He himself never learned to drive, so he cannot drive home, and knows nothing about the other two. The second and third logicians both walked to the bar, but know how to drive. Each individually cannot drive because they have no car, so their answer to the bartender is conditional on whether the first logician came with a car, which was not revealed by his answer.

At minimum? Zero.

The first logician was driven to the bar by his friend, who then biked home, leaving the car in a local garage. He himself never learned to drive, so he cannot drive home, and knows nothing about the other two. The second and third logicians both walked to the bar, but know how to drive. Each individually cannot drive because they have no car, so their answer to the bartender is conditional on whether the first logician came with a car, which was not revealed by his answer.

At minimum? Zero; it's possible none of them ever learned how to drive, but have not shared this information with each other. Thus, each knows he cannot drive, but is otherwise unsure.

At minimum? Zero. The first logician was driven to the bar by his friend, who then biked home, leaving the car in a local garage. He himself never learned to drive, so he cannot drive home, and knows nothing about the other two. The second and third logicians both walked to the bar, but know how to drive. Each individually cannot drive because they have no car, so their answer to the bartender is conditional on whether the first logician came with a car, which was not revealed by his answer.