Another Oil Thread - Sorry

Recourse is the thing that came to mind throughout this thread. I know of two instances where Quaker State and Chevron sold mis-formulated oil. Quaker State stepped up and informed customers, pulled and replaced product, and paid for engine damage. Even to retail DIY customers.
Costco has a great return policy, but I've wondered about what they would do about consequential damage from oil. Wouldn't like to be the first one to find out, but if I ever had a suspicious engine failure, I would begin documentation and oil analysis immediately. There's some interest in the Volvo forum I follow about the Kirkland oil, but nothing definitive about performance or horror stories. Modern European engines are difficult to keep within spec, as the ACEA specs aren't linear, where the higher classification numbers is better and safe to use.