…as for the engine knocking, I’ve always used premium fuel (93 octane) and never had any issues (in 89,000 miles). Expensive …YES, but so is the vehicle.
To me, it’s like eating a Big Mac, large fry, and washing it all down with a Diet Coke. What’s the point?
By the way, the Owner’s Manual recommends premium fuel. Hope this helps you. Drive safely.