This a contribution for the Paula problem related to used oil:
The best solution for used cooking oil is a recycling culture helped by city councils and gas stations.
The used vegetal oil has a direct recycling way to BIO-DIESEL.
I'm sure that , in the same way we learned to recycle cristal , paper and others, we can learn to recyce oil.
We only need a bit of regulation by our city councils. Just local containers networks and Petroleum Companies collaboration
Yes, I thing the best site for contaniners are the gas stations. The petroleum companies are who perform that process and obtain benefits with the transformed product so they can do the job for free.