Had a tire with a slow leak so I had to add air every few days for a few weeks. Then all of a sudden the leak stopped without any intervention by me. Any reason for that?
Someone called Car Talk with a similar issue a bit ago. Their answer was that it didn’t stop leaking - it’s just a slow enough leak that you don’t notice it most of the time.
Is that possible in your case?
-D/a
This is likely due to a faulty valve stem, or a small puncture through the tread that has subsequently become plugged. It will likely start leaking again, so it would be a good idea to have it inspected and repaired before it goes out at 65 mph on the highway.
Stranger
In colder temperatures, a couple of my tires lose pressure. I need to add air every 10 days or so.
They’re fine once the temperatures climb above freezing.
I attribute the air loss to having aluminum rims and the effect of cold on the rim expansion / contraction.
This type of air loss can often be reversed by having the tires removed and reinstalled - the surface of the rim where the tire bead seats itself can be cleaned to remove any dirt or surface imperfection. But air loss with these rims is not uncommon where temperatures get quite cold.
My first BMW I found that in extreme cold I could get a flat tire. Eventually a helpful tire garage said it was due to aluminum rims contracting in the extreme cold and breaking the seal. When he remounted the tires with some sealant goop, this solved the problem. Apparently in Europe they don’t seem to tihnk this goop is needed. I guess it doesn’t get taht cold outside of Finland?
Tire leaks often get worse depending on how the rim is rotated when you park.
That’s why a annoying slow leak turns into a flat at 7AM when you need to leave for work. It’s your bad luck that the tire was in just the right position to leak out while it was parked overnight.
I had a nail in my tire for a while before I found it. If I parked with the wheel in the right position, the nail “plugged the leak”. In a different position, it leaked.
As others have noted, whatever appears to have fixed the issue is probably temporary. If you don’t get it fixed properly, it will come back, most likely at the worst time.
as predicted the leak is back. But I did discover that Sheetz has free air. 
I will get it fixed this week