My daughter is home from college. It is 10 degrees outside so I did not want to do an oil change. For the first time in 30 years, I went to an instant oil change. In addition to changing the oil, they look for other issues including improperly inflated tires. They concluded the tires should all have an extra two pounds of air to compensate for the winter temperatures. This all occurred on mid-day Saturday. Fast forward to mid-day Sunday and one of the tires is 100% flat. I thought maybe I drove over a nail on the way home so I inflated the tire and told my daughter not to drive it until I could take the tire to the shop to get it checked. Now, it is Monday and the tire is still fully inflated. I know holes do not magically heal themselves. It seems unlikely but I wonder if the valve could have stuck open a little bit and drained the tire? I would just take it in and have it checked but of course everything is closed today.