I realize that all have conditioners. The thing is you only want as much as the seals need, not an excessive amount and any more swelling than needed is detrimental.Dave9 all motor oil has a little bit of seal conditioning seal agents in them. All of the oils have that in them.
Only difference is high mileage oil has has higher percentage of them.
Dr Molakule on here who has blended oils has told us that all motor oil has seal condioning additives in them.
By the way... I really do like your posts on here. You add a lot of good thoughts on here.
There seems to be some gross misunderstanding on this forum. You do not want your seals dimensionally swollen, nor any more pliable, than necessary to do their job. Any more than this, increases the wear rate. Wear them, and keep using HM oil and everything may seem fine because they're still swelling more than their dimensions would be otherwise, but you have dimensionally altered and degraded the seal at an accelerated rate. If the engineers wanted the seal to be larger and lower density, they would have used a larger and lower density seal in the first place.
At the same time, using too little seal swellers is detrimental too. You should hold off until you have a reason to use it, and if you're paying close attention this would also mean, using a few quarts, % of HM oil not a switch that added more seal sweller than needed to combat the beginning of the condition.
I'm not talking about total engine devastation overnight, rather that in the long term, it is a "little" bit worse to use HM oil with extra seal swellers than not to, until it's needed... shades of gray, minute differences, is pretty much what all these "which oil should I use" topics are about unless they want to make a drastic change. People want some miracle in a bottle that solves everything and odds are, the bottle is not the solution. Heh, that has a crossover to drinking but I digress.