Q.S. 20k oil but I would change it 5-7k, just a few bucks more than Supertech but less then the rest.
Honestly Supertech would probably do you good also.
I had an increased oil leak on multiple vehicles after using it. Maybe cleaning to good around older seals.
Maybe not as good seal conditioners.
Not sure but I like Mobil 1 just not on higher milage cars
A battery can have a dead cell and check good.
Have someone try to start it while you have a Meter on the battery, it id drops below 9 or 10 it's the battery.
Weeks ago my daughters battery checked 12.4 try to start it, it dropped to 6 something
35 years ago I used to drill 2 small 1/8 holes in the flange so when it was closed it still slowed slightly.
Did it help couldn't tell.
But in my mind if my thermostat ever stuck closed I would have some water circulating to help prevent overheating