I would recommend getting some useful life out of the current oil fill, then start an auto-rx cleaning regiment on the next oil change. The Castrol High mileage blend is not a great choice for a host oil to maximize Auto-Rxs cleaning ability.
High mileage oils typically have some components that tend to swell polymer oil seals. Unfortunately most times valve stem seals have a hardened glazed oil residue coating them. Therefore you really dont get the benefit of the seal swelling.
We find it more effective to dissolve the glaze off the seal and dissolve the grime on the valve guides and let the seal rebound on its own. If the stem seals are severely worn, replacement may be the only option. However, in most cases we can at least revive them to a more acceptable level from cleaning.
