So based on the list of suggestions, its wide open! Good points made in comments. If it's down to single digits then just know your locks can likely freeze, windshield will ice up, a weak battery will become a dead battery, and questionable tires in the summer become downright dangerous in the winter. Which car you choose is important but probably not the most important. For any winter driver it's critical to keep up with maintenance. Above all that, any winter beater depends on the driver. Leave earlier than usual, keep speed DOWN, drive carefully, and silly as it sounds...dress for winter! California winters generally have no comparison to what you hardy souls in the mid-west and east routinely endure. But having made many comparably icy treks across the snowy +7000 foot elevation Sierra Nevada mountain passes, my favorite observations are seeing someone standing on the side of the highway, blankly looking at their low-slung 20-inch rimmed sports car, wearing a short-sleeved t-shirt, basketball shorts, and soccer sandals, wondering why they slid off the road and can't get over the summit. Happens far more than one would believe.....west-coast city folk!