The reason many shops will not take waste oil (mine included) is that to be frank we have no clue what is in it. If there is chlorine in it (which waste oil companies test for before they pump the tank out) that turns it into hazardous waste. If there is too much water or antifreeze in it or gas or diesel that turns it into hazardous waste. Couple that with the fact that I have to pay to have waste oil disposed of and no I will not take waste oil off the street. Most municipalities will accept waste oil from consumers in PA.
This right here^^is why I will not accept used oil off the street, They use to pay for used motor oil....But I don't see that ever coming back.
Don't use a waste oil heater for the whole 30 days of cold weather we have here, If a waste oil A/C system is ever invented.....