This has me perplexed.
One of my relatively low milage (3000 mi) tires loses air pressure intermittently - every 5 months or so I will go out and the tire will be almost flat - over a short time period ( i.e. a day) it loses pressure to the point it is flat. I'll pump it up and it will be fine for another few months - and then suddenly it is flat again. I had the garage rotate the tires last spring and they checked the tire - no nails etc and replaced the valve stem. The only difference after rotation is that the tire leaking is now on the back!
Nothing special about the car or the tires - standard Mercury Mystic Sport
The car is in a garage, so it is not kids.
Suggestions?