Valvoline makes some good oils, although not all appear suited to extended drains.
I had a great UOA from my BMW using Maxlife Nexgen SN 10W-40, although I ran it only 4K. There was plenty of residual TBN to have easily done another 2-3K or more, and wear metals were very low.
I recently had a UOA done after a 5K run of Synpower SM 10W-30 in the Forester.
Wear metals were low, but so was TBN.
The oil could probably have been used a little longer, but maybe not much.
SN Synpower might have better TBN retention, particularly since Valvoline claims that the oil meets Dexos 1.
I've been happy with Maxlife, but will probably not use Synpower as a matter of preference after my current mini stash of it runs out.
I would buy and use Synpower again at a low enough price and I'm interested in seeing some UOAs of API SN Synpower, which may show much stronger TBN retention than I saw with the SM.
Synpower is very smooth and quiet in the Forester.
Variety is fun, and using Valvoline is something new to me over the past year or so.
Try some and see what you think.