I had my Trans Am less than a week and someone stole the valve covers. They scratched the fender and set off the alarm. I saw a couple of kids riding off. Imagine laying out 37K for a car and having someone else scratch it in the first week. It sucks but that is how people are.
What makes you think the mental midgets who take them are the slightest bit choosy? I have had the black plastic ones taken and all the way up to some fairly nice ones, but none of them were expensive. Since often only one or two are missing, I theorize that they are many times just kids who want new, cleaner ones for their bikes. If they can squat down next to your tire and not be seen, they are gone! The only time I had success in keeping some for a really long time, I used the hexagonal chrome ones and tightened them with a small crescent wrench. Most of the kids just use their fingers to try to get them off, but I decided it was too much trouble, IMO.
The kid theory makes sense. I've never had my metal valve caps stolen but my father's car is constantly being targeted.
I just bought a 2011 Prius. I traded in a 2010 Scion Xb that was getting about 25 mpg average. In all of my other cars, the caps had been stolen, even the type that lock. Some SOB used a pliers to pull them off. Today I took off my Nitro-Fill caps and put on plain silver plastic caps, just to avoid the aggrevation. It does not pay to have something nice anymore. I wish I could catch him.
I have the green ones from Costco. I love it and it goes great with my silver Prius. And if you ask them, they'll give you some for free.
That beat mine. My blue valve caps were removed at 500 miles. I just went inside and grabbed another 4 and replaced them. Thief hasn't been back since.