I agree - don't bug shops for their waste oil. Enforcement varies by state, but the US EPA classifies auto/truck repair facilities as 'waste oil generators' and as such these shops are regulated as to how they can dispose of their oil, etc and are buried in government paperwork that tracks the 'waste oil'. Chains, dealerships & larger shops tend to get regular visits from EPA or their state level representatives checking their methods and auditing their paperwork. Its a big enough hassle without the added risk of kicking a few gallons to some local joe. On the other hand, you might want to look at other unregulated places that generate waste oil. As an example, rural airports with a population of small, light aircraft will have a groups of plane owners that maintain their own aircraft (ie: change oil). Stay away from the FBO (the professional shop onsite) as they face the same regulations as the auto shops. The hobbiest owner/pilot will generate 1-3 gallons of waste oil per oil change. Additionally, aircraft are 'sumped' before flight (a few ounces of fuel is pulled from each tank to be tested for water content) . Most old school pilots just throw out the sumped fuel. A clever 'ramp rat' will furnish a collection barrel for waste oil and a collection pail/small drum for waste sumped fuel. A fellow A&P (aircraft mechanic) who drives a w126 yearly collects several drums of WMO and about 100 gallons of waste fuel (kero, JP4, Jet A & avgas). He also collects left over/stale 2 cycle fuel in fall & spring (most ultra lights are 2 cycle). He rarely has to buy fuel at the pump. His benz is pretty ragged, but it starts & stops OK so he uses it for his daily driver. I don't use WMO/WATF, etc in my benzes, but I do have a small diesel rescued from an old mower that loves the stuff. It's perfomance isn't critical, and it was free.