I just perchance a 1936 Olds Touring Sedan with all original flat 6 cylinder engin. (Running but barely) First vintage purchase so I don’t know much about older cars. I need to change this black dirty oil ASAP. Do I use SAE 30 with some sort of additive (HTDP?) How many quarts? Where is the oil cartridge or filter, I could not find it underneath? Would Napa have a replacement for me; do I need to give them a Part number? Does anybody have suggestions on mod kits for this old engine? I would like to keep the original but improve its performance reliability. Need help badly Andrew from Delaware