Don't worry about AmsOil. If it leaks, there's a mechanical reason, not that the oil did anything bad to the seals -- it's been years since synthetic manufacturers came up with the right formulation to keep seals from shrinking. The only time that I ever encountered sudden leaks after starting synthetic oil was when I first used Mobil-1, back in the late 1970s.
I've used AmsOil since the early 1980's on all my 240s (1978, 1980, 1983, 1984, and two 1993's), all bought used with anything from 70,000 to 180,000 miles already on them -- engines regularly last past 300,000 and in every case, I got rid of the cars because they rusted away (that's N.J.), not because of engine problems or emissions test failures.
Trust AmsOil -- if your car was already full of sludge, the AmsOil would get dark fast -- it's cleaning and keeping the dirt in suspension, and a simple oil filter change would be warranted (do it often, just adding some oil each time). But once the engine is reasonably cleaner, I change my AmsOil every 8,000 to 10,000 miles, and the engines' interiors always stay clean (I mean really, really clean).
Another benefit I've found is that the Flame Trap's screen and trap "box" stays clean -- you'll find (after using AmsOil a while) that you don't have to worry about changing/clearing it. But you have to give the AmsOil time to clean out your engine first.
Here are some photos of a look inside my engine (the valve train, seen through the oil filler hole):
My '84 (started with AmsOil at 80,000 miles, now has 230,000 miles)

One of my '93's (started with AmsOil at 120,000 miles, now has 190,000 miles)

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