In the past I have taken a bottle of vegetable oil as it comes from the store and burned the old oil in the campfire.  This year I am going on a 15 day trip where we are planning to eat fish about a third of the time.  Wanting to keep the food pack as light as possible for such a long trip I plan to reuse oil by filtering it back into a spare bottle.

I too would be interested to hear from more "learned" QJ'er's