Have not read all the pages of this thread, but I would never use RTV on an oil sealing gasket, as was suggested on page 1. If you use even a hair too much, it will squeeze out on the inside, and can end up clogging an oil passage. It's not unusual for an amateur to use so much RTV, that it ends up clogging the oil pickup tube screen. Any of these scenarios will destroy the engine in short order. Not to mention that next time you change the gasket, you'll have to scrape off the old RTV, and doing so without getting any bits into the engine is a challenge.

If you must use a sealant, use something non hardening, like Curil-T. Not only will it be safer for oil passages and screens if you apply a little too much, but it also has the ability to expand and contract slightly (it's non-hardening) to account for temperature changes and shrinking/swelling of the rubber gasket, so it provides a superior sealing ability as compared with RTV.

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Current fleet:
1998 E300 turbodiesel
2008 E320 bluetec - leaky oil cooler seals replaced
2012 S350 bluetec
2015 GL350 bluetec

Sold:
1996 Passat TDI
1997 E300 diesel