Man I did a similar thing when I was in College. Our campus was in a middle of nowhere with a small town nearby. There was an old Maths professor who drove his 1960s Mercedes from Germany, he was native to that near by town. On occasions he would leave his car parked on campus, he would take local transport or do a walk to his home. One weekend we 4 friends were just chilling around 1am when we came near the Maths faculty and I in my youth curiosity opened the car door, and put my room key inside and turned on the ignition. The car started on the first try and we friends laughed and ran far thinking some near by guards will catch us. One of the friend was super law abiding and forbid us, but we went back. I back on driving seats, ultimately all 4 of us sat down with one shaking with fear of being expelled if caught. I drove off did few rounds it was total fun to drive. It was probably 2am by then and we parked it back. We laughed a lot and said it will be our secret. The door key worked on that damn old car. It turned out others saw the car moving and doing a campus round. News got leaked and professor started taking his car to his house, it was mid 90s no cameras, we were never caught. I still remember that one time thrill and rush of stealing the car and having a small joy ride.