I now have the same questions about the rear main seals as "Machine Man" brought up in my earlier post at:
http://www.brickboard.com/RWD/volvo/1388936/940/960/980/V90/S90/elring_rear_main_seal.html

I replaced the rear main seal a couple weeks ago in my daughters 1993 940 type L non-turbo engine (in a 1991 740 sedan).

In 2005 I put the engine in the 740 and replaced the rear main seal with a 93mm Silicone Elring seal. I couldn't believe how hard and cracked the Silicone seal was when I replaced it a couple weeks ago. It was not flexible at all and only had 57K miles on it. I replaced the seal with a Viton 93mm X 110mm X 7mm seal. It fit very tight in the housing and was okay around the crankshaft but I wonder if a 92mm Viton seal would have been better. I have no idea what size was in the engine when I replaced it in 2005. I don't think it leaks (the car is a couple hundred miles away) and unfortunately I didn't measure the crankshaft where the seal was.

I can't find a supplier of 92mm seals in Viton or Silicone and my local Volvo dealer only had the redish brown seals so I assume they are Silicone. I certainly would never use a Silicone seal for the rear main seal again after my experience above. I got the Viton seal on ebay. It was by Elring.

I removed the seal housing from two junker engines I have, a 1990 B230 and 1991 B230, both type K engines, and they were 92mm.

So, I have the same questions now that Machine Man had in his answer to my earlier post i.e. which engines had 92mm seals and which had 93mm seals?

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Mine: 2-940s, 3-740 and 1-940 parts cars, and 3 John Deere 630s, dtr1:3-940s, dtr2:2-740s