Ah - But my concern is that a “minor” mutation - which we know “never” happens with microbes in the wild - lets the micro start eating petroleum-based products, not just free-standing oil.
Just try to not imagining all the possible foods: Rubber tires, asphalt, petroleum-based clothes, rubber hoses, o-rings, seals, paint, fan bets, tie-downs and nylon hoses, tarps, glue, sealants, gasoline, ......
Might be all sorts of profitable “end-of-the-world-as-we-know-it" novels in that story.