I used to think that you can compost all kinds of food waste, including used cooking oil until I discovered Compost This.
It reported that cooking oil attracts rodents or other undesirable creatures to your compost heap. It can also displace water which will slow down the composting process.
Leftover food you are not supposed to add to your compost pile are:
You can read their reasons for not using these leftovers. Now that we know that, what can we do with the used cooking oil?
You can find the answer by doing a search on "cooking oil" at "How Can I Recycle This?"
So, before you throw away any leftovers, remember that there are many people out there who are very eager to share their tips and tricks for reducing waste.