The basis for my comment about the Mobil 1 came from comments a chemical engineer friend of mine made; he knows an engineer that works for Mobil (also a Chem Engr)and that's what he said. Quite frankly it could have been heresay, but I regard my source highly enough to pony up an extra $2.00 per quart for the RedLine oil. What was further bantered about is that Mobil 1 will now quite probably come down in price a bit in order to compete with the dino/synthetic blends being brought to market. In my area Mobil 1 has not varied in price, so I can't explain MikeM's experience there.
Now, as regards the sludge barrier that gets broken through, I don't know if I buy that, MikeM. The service records for my '88 300TE showed a very good oil change history, about every 3k miles. I've never read a word about such a phenomenon, and I've read everything I could get my eyes on about synthetics for a good twenty years. All of the articles seem to have concluded is that the oil leaks begin simply because of synthetic's superior flow characteristics. With an older car, my understanding was that the decreased flexiblity of the seals prevented the seals from compensating for the better-flowing synthetic. However, you sound like someone who knows what they're talking about, and indeed what you've said sounds quite plausible, so I guess I'll have to consider this possibility.
Lastly, Red Line recommends extending the oil change interval to 15k miles, with a filter at 7,500. Sounds like they've got quite a bit of confidence in their product, but that sounds like a bit long to me, no?
Hope this helps, and thanks MikeM for the insights/feedback.