Q: Something very annoying is happening to my cars that are parked outside in the cold. (It doesn’t seem to affect those in the garage). When I start the car, the “low tire pressure” warning light comes on. To fix the problem, I have to put a few psi of air into the offending tires. So, where did all that air suddenly go overnight? When it warms up, will I now have too much air? What about the tire stores, which offer to put nitrogen into my tires for a hefty fee? I purchased a 1-year-old vehicle with the green valve stem caps, which I think signify “nitrogen only.” What if I add regular air?