I don't have too much experience tearing down engines I've run a long time but my '90 Integra saw Mobil 1 and then Castrol Syntech (when it first came out) for most of its 90,000 miles with me and at around 60,000 miles, the cam seal leaked ... but this was notorious with these cars. I can't fault any oil.
My '95 Civic used no oil for the first 100,000 miles which was almost exclusively Mobil 1 5W30. At 95,000 miles I switched Valvoline Synpower and consumption appeared ... about 1/2 quart in 5,000 miles. I switched to Red Line at around 103,000 miles and consumption (eventually) returned to zero.
No signs of any leaking whatsoever.
I think that some of the synthetic base oils have a little bit of natural detergency (esters & alkylated aromatics), but I don't believe they can revive a basket case. Also, a lot of oil burning is from rings and scored cylinders and no amount of seal swellers will correct that.