0W30 is OK for winter use in cold climates, but I would not use it south of Chicago. I used the 15W50, but it is no longer C rated for some reason -- use the C rated mobil 1 and you will be fine.

For diesels, you must use something with a C-rating (current is CI-4), and on any of the older ones, you MUST use CH or CI rated oil to suspend enough soot to make it last long enough -- the older engines soot up faster. If you want to do extended (more than 3000 miles) oil changes, get the oil tested and watch the soot % number. Change before you get to 4% -- it will get flagged on the report when it gets high.

For 60x and newer diesels, 6000 miles is what I aim for, often run more. No problems at 240,000 miles.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!