Not sure if the A/C on the 451's is the same as the 450's, but there is a suggestion in the owner's manual of the 450's that is well worth noting. They suggest running your A/C for about 15 minutes/week during the winter months. If you don't do this, there is a good chance you will LOSE YOUR CHARGE on the A/C over the winter, leaving you without cold air the first time you need it in the spring. The charging is not that expensive, but its good to know you can avoid it by going through this weekly drill in the winter. I know this is true from personal experience

!
Ron Gaus, asmartcar.com