Synthetic oil will only cause a leak if the only thing keeping oil in the engine was sludge plugging the leak.

Thirty five years ago, when Mobil first started selling Mobil 1, there was a problem with rubber seals shrinking when Mobil 1 was used in an engine with lots of miles with dino (actually, the dino oil caused the seals to swell, and the wore to fit. Mobil 1 reversed the swelling, and they leaked). The problem was solve THEN by adding a small amount of seal softening agent, and the problem was gone by 1976 or so.

The stories still abound, however. Just goes to show, eh?

Anyway, if you switch, change your oil filter (not the oil) after 1000 miles as it will be completely full of crud that has washed loose. If the engine has hundreds of thousands of miles, I'd do another filter change in another 1000 miles just to be safe, filters are cheap, MB engines are not.

Peter

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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!