It's a minor point, but proper circuit design is to select an electrolytic capacitor rated about 20% higher than the applied voltage. In this case, being a very low demand situation, it won't really matter much though. It would certainly outlast the remaining life of the car itself.
2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg
And remember folks, Only You Can Prevent Hilliary.