I switched the 260E over to synthetic at 184,000, it now has 302,600 miles and no leaks. I use oil, but don't leak it. I also switched to Mobile 1 0W40 for the upcoming winter (or lack of) and my consumption went from about 850 miles per quart to 1,500 miles per quart. Go figure.
Interesting about Castrol, I just bought 2 cases!
01 S55 AMG Silver
01 CLK55 AMG Silver