>>1964887I'll sleep in subzero temperatures without a heater if i have to, but it sucks.
0 degree bags are not bullshit, they are definitely a valid gear choice. In the van I just use regular blankets, but they can get drafty. Get a little buddy heater, it will make you much more comfortable.
But, it's always going to be warmer in an un-heated van than it will be outside.