I find the 912 typically burns 12/hr rather than the book 15. Having spoken to many pilots and instructors who operate this engine, they all tend to agree that at around 4400rpm you get 12/hr (obviously with speed dependent on the airframe).
Also, with autolean, it is more like the theoretical engine described by the OP.
I'm a big fan of lycomings and continentals, but 100LL won't be around forever, so it's great that there are already alternatives emerging.
Edit
@Jan Olieslagers I think workinghard was making the point that an aircraft flying for 50 hours at around 100mph then having a service is the same at the OP's car being serviced at 5000 hours.