I don't know for sure they really do have these seal conditioning esters as mentioned. IMO, from what I have seen between penz and valv high mileage oils, neither seem to clean very well. the detergents are lower, and I'd say for good reason.
IMO, if you were to put esters in the oil, it would tend to clean things(according to some here) and if you clean an old valve stem seal for example, that has been crudded up, it would create a smoker letting oil pass by the harden seal. This is why I noticed that those oils didn't clean as well as the full synth's that is known to have esters in them.
Also it appears that from some analysis, the high milage oils have a lower level of detergents. By doing this, it would not clean but also allow the existing crude to maintain the current seal properties using such.
Now based on what I have seen in sludged engines, There was several mechanics trying to head off these sludge puppies as when they saw one looking like it was getting sludge, they'd put in half a qt of trans fluid which dramaticly increases the detergent levels. This would in fact clean a sludged engine, BUT, in doing so, within a 2 wk period, the car came back smoking, where the detergents had actually cleaned away the crud and left the harden seal.
Look at those pics where I left the crudded up valve stem seals in each oil for 2wks and you'll notice, synth's, cleaned pretty good where as both high mileage oils did very little.
Cleaning and Seal conditioning