There's also environmental factors to consider in anything physical, sure, you changed your oil, but what do you do with the oil now? There's no electrical pollution in running a server.
If you live in the US. Auto parts stores take used oil. As do Walmarts with auto service centers. I’ve never had an issue.
I do not. Where I live you buy new oil getting a receipt for a change. You get $5 back if you bring back the used oil, but if you lose the receipt you have to throw the oil away. It's... a really bad system