Burning the spare tire can keep you warm. Some diesel or gas and a road flare. Let the air out or hole it first.
My winter list….. in the vehicle.
Pak boots with wool liners – winter mittens
Mainstay bars and water rations
Axe & knife
Mapp gas torch – lifeboat matches
Led headlamp with lithium batteries
Roadflares – safety vest
Blizzard mylar sleeping bag
WW2 wool sleeping bag and bivy sack
Backpack and assorted tools wrenches etc. extra wipers.