I was using rotella 15w-40 and just recently Mobil Delvac 1300 15w-40. 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, 10w-30, so the rings can seat a little better. Wow, the 10w-30 really woke up my 1984 VW diesel...