waste oil for heat, is it environmentally friendly?
 

I have a bunch of used car oil sitting around. I was going to offer it to the local guys to see if they could use it for heating. I am curious, is this a good use of it? I suppose it depends on the efficiency of the burner. Or, should I just go drop it off at a recycling center instead? I'm not really sure what the recycling center does with the oil.