Is it easy to get used cooking oil? Aren't most restaurants already selling their grease?

Cooking oil

It depends on your community and how much you want to go knocking on doors. It would be a good idea to investigate used oil sources before you commit to making biodiesel.  We have found that there still remains surprising amount local, inexpensive restaurant oil and that restaurants are often more concerned with finding a guaranteed reliable pick-up than extracting maximum price for their waste oil. If you own a restaurant you are in a perfect position to make your own biodiesel.