this is a DIY bio-diesel site. The directions are for a 1 liter bottle worth. Anyone can figure out how to increase the recipe.
http://biodiesel.infopop.cc/6/ubb.x?a=tpc&s=447609751&f=719605551&m=857600061 Note that this is not for used vegetable oil. Instead it is for new vegetable oil. Post SHTF you can plant extra corn to make oil out of.
Black sunflower seeds have more oil per pound so that might be a viable self seeding alternative.