I asked my mechanic the same question when I was pondering the conversion and he replied that if I switched back to dino oil right away, the leaking caused by the synthetic oil *should* stop.
When I switched from dino to synthetic in my '89 300E last year, I had no leaks. My brother has a '77 280E and he recently switched as well, with no problems. From what I have heard it is basically a gamble, although the odds seem to be on your side. Good luck!
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired
"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon