When you change the oil in a diesel it will be "old and black" again in about 100 miles. There's a lot of soot blowby in a diesel that really makes the oil get dirty. That's why you need something diesel-rated (a good detergent oil). A good oil will keep the soot suspended so that if you change regularly it will be washed out with the old oil.

Thus the recommendation to warm the engine up completely (like on the highway) before pulling in to change the oil. This helps the oil to have maximum suspension of soot when changed.

You're just gonna hav'ta choose your own oil brand, 'cause if you ask here this thread will grow to 500 posts in a weekend.

Ken300D