TLVR

The last time I checked the tire pressure of my spare donut was 6 months ago. When I checked it-sure enough it was down about 10 lbs. So brought it back up to the recommended 60lbs with my handy air compressor. Adding air was no problem. However, immediately afterwards when I slightly moved the valve stem laterally -a strong hissing sound indicated there was a leak around the stem. Since this spare had never been used I decided to see the dealer- not wanting to have a defective spare sitting in the trunk! I asked to be given a new spare since I did not trust repairs on a new spare. Dealer decided to check it out and found that the valve stem was partially stuck and had not fully been pushed up through the rimhole. No wonder it did not seal properly. They pulled the valve fully through as required and declared all was fixed/no more leaking. We shall see and I will keep a close eye on the pressure retention. This might seem to be a trivial matter but maybe you should check your spare as well. Hate to be needing it and find out the hard way... Actually one service writer had the audacity to suggest that I might have pushed the valve stem inwards a full inch when I added air!! This resulted in a verbal spanking which he deserved. BTW. Which pressure gauges ,pencil or digital, are considered reliable and accurate?? Thanks for your help