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Soil microbes actually do break the oil down over time if the dose is small enough. People poured waste oil along fence lines instead of running string trimmers. Some traces of lead and other metals from engine bearings will persist. Now of course places gladly accept it for free and will sell it when they accumulate a large enough quantity.
Valvoline doesn't even dig for oil, they just recycle used oil, and truth be told their oil is fucking fantastic at non-extreme operating temperatures. IE at less than 270 degrees f. Chances are if your oil temps are that high, you have bigger issues, and should remove the leaves from in front of your Porsche's radiators.
Real Porsches didn't have radiators! Oil stayed below 270 in part because of the 13 quart tank for the dry sump system. (Technical people might claim the oil cooler is a radiator but I fart in their general direction.)
993 turbo for life, a real man's car, that thing will crush the turds in your intestines with the amount of butthole puckering.
Modern oil is full of synthetic chemicals that microbes have no evolutionary experience with. These chemicals can be antibiotic, toxic, and highly resistant to oxidation. Not to mention metals picked up by the oil.
I did mention metals accumulation :) Most of the detergents are metal salts as well as the metal that wears off of bearings.
I'm much greener now and give it to a place that burns it, sending the various metals into the air.
I’ve seen auto repair shops that heat their building with used motor oil. Pretty convenient for them.
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