2015 Tacoma 4.0L 1GR-FE Amsoil SS 0w-30 31.6k mi OCI

Legitimately didn’t know you could do this
Yup. Most auto parts stores will take your used oil for recycling. Some not all can take filters.

Totally agree with dropping the OCI down; 31k is obviously too far. Despite the TBN still being good, the oil has thickened out of grade even at 24k, indicating to me that it is nearing capacity to absorb impurities. 20k seems reasonable to sample 2-3x and if it all shows good that would be my mark.