You must be talking about auto parts stores? I buy my batteries at costco and have for many years. They just charge $15 core charge on any battery they sell. Last one bought in 2024 was still just $15 core charge. They don't need a receipt. They just look it up in their system.
It a good oil. Been using Valvoline synthetic 5w30 oil in my 2007 Corvette 6 speed manual so far all is good. I usually only drive it about 2000 miles a year so I'm just changing it once a year. Kind of surprised at the 1610 Ca. It is a little higher than I remember.
I've just always used Valvoline conventional A/T fluid Dexron III, Mercon the stuff in the (blue bottle) in most vehicles PS system including Toyotas. Never had an issue with it.
It could be a bad oil sensor or it could be oil drain back issues on that engine. After extended spirited run some engines can run the oil slump low. Do you know if it is a pressure or level sensor? What is the oil capacity of that unit?