There was a thread a long while ago where I called the Oil Life Monitor a Kilometer Reader and there was some back and forth on it. I put it to a test. I run Amsoil Signature Series in both my trucks (5W-20 in the black one and 10W-30 in the red one) and I wanted to see if this thing was even close to accurate, so I waited until the "Oil Change Required" message came up on the dash. It took just over 9000 KM. I even drove around with it on for another few hundred KM. So I took a sample of my oil and sent it in to Oil Analyzers to be tested.
They sent me back this:
Good for continued use. But my Oil Life Monitor says I need an oil change, weird.
I will take another sample at 16 - 20,000 KM and see what they say.