I buy eucalyptus oil from the manufacturer in my area, it is made from several varieties of local eucalypt trees, and is produced using distillation. I also have made my own by boiling leaves and collecting the oil from the steam. This takes a bit of time and you have to have a large amount of leaves, (not a problem when you live in Aus). I find the type of eucalypt makes a difference to how much oil you can get out of it, older leaves are better than younger leaves as well.