I have an MZ3 that's been making metal in the filter for the last few months. It hasn't affected power since the dyno still shows 133 WHP. I currently use Pennzoil Patinum 5W-30. I tried changing it up from the 5W-20 I was using previously. The engine is also burning about a liter every 5000 km. The Blackstone Labs reports I sent out say that there's no significant traces of metals in the oil. Do the Duratec engines burn oil naturally? Or should I be looking at rings and a hone?