If it's truly pinging or knocking and you're actually able to hear it then I doubt bad gas or environmental factors are the issue. Octane and environmental factors might be contributing to the problem but these cars will knock bone stock right off the showroom floor on 87 octane and you will not even notice it happening. That's why you make more power on 93 octane vs 87 octane.
So bottom line is this. If you're hearing a real knock then your car is not picking it up and making the appropriate adjustments to correct the issue. That would mean there is another issue with the ECU or knock sensor which would need to be addressed at the dealer. It seems like a faulty sensor would generate some sort of code. Take it to the dealer and have them drive it to see if they think it's really knocking. That or test drive another car and see if it does the same thing. These engines are exactly quiet under WOT when it get above 4k rpms. They're pretty loud.
Displacement makes you complacent