Has anybody here tried those Legacy Gas Saver Valve Caps? See here.

They are made for 36 and 32 psi.

The 36 will turn red from green at 31 PSI. The 32 will turn from green to red at 27 PSI. They are cheap at Wal*Mart, $4.95 for a set of four.

I put them on a few of my cars, but I am not so sure if it's a good idea. Some people have had trouble with them where they will leak and cause the problem they are designed to prevent. This is according to old messages (several years old) in other forums. Hopefully they are now improved, but since they are made in Taiwan, I am not sure if I have a lot of faith in them.