Years ago I had a fleet car (Chev. Cavalier) that would have a tire go flat at random times. We never found a leak so we would pump up the tire and check the air pressure daily. It never went down a pound until days later when it would again be flat. Out of other ideas, we inflated the tire without moving the car. The steel wheel had a weld that would leak air if the weld was on the bottom of the wheel when the car was parked.
A new wheel solved the problem.
The answer to 80% of BITOG questions: Read the book, follow directions.
Changing oil is not maintenance. Maintenance is the science of inspecting equipment to find and fix things before they break.