Mine hasn't missed a beat in 35k miles. It certainly doesn't use any oil, not a drop.
I change the oil every 8k miles and use only Mobil 1. The dealer thinks I'm mad for coming in 4k miles early. He told me that the long service interval is OK because the motor contains 8 litres of oil. I'm not so sure.
The engine was recently likened to a i-4 in a UK publication but in my view it is very sweet, albeit not a BMW i-6. The V-6 was awarded 4th best engine in the world in some US report.
Transmission is a joy to use.
Try this link to a past post for a rave review:
M112 Engine Review