I was using rotella 15w40 and just recently Mobil Delvac 1300 15w40. My motor has only 2700 miles and I noticed it consumed the most oil with the Mobil. I ended up switching to a lighter weight oil, 10w30, so the rings can seat a little better. Wow, the 10w30 really woke up my 1984 VW diesel N/A motor. My motor revs so much faster, it's great! Also, the oil I ended up using was Mobil Clean 5000, because it has a CF/CD rating. I bought it at Walmart but noticed on the back of the bottle label that nowhere did it include that CF/CD rating. This was noticed on the 1qt size bottles and the 5qt bottle. On Mobil's website it is stated that it is CF/CD rated. I called Mobil up to speak with a technician and he told me that the website is current and there hasn't been any formulation changes. He also had a bottle of the Mobil Clean 5000 in hand to state that the bottle had the CF/CD rating on the back. What I find weird is the bottles at Walmart fail to include these CF/CD ratings.