Arco is my go-to brand. I can try another brand, and I expect that a higher octane gas WILL make the ping go away. But I understand that the higher octane inhibits early ignition, and so in this case, masks the timing problem. I think it's obvious it needs an updated flash, and supposedly that's what they did at my first service, but the ping is still there. I'm concerned since it's been doing it since new, and I know that early ignition is not a good thing for the life of the engine.
I'll do your suggested experiment, but here's the thing: I've had cars that ping, and cars that don't ping, and generally I've run them all on Arco gas. So there's that. The ones that have pinged, the issue was never sufficiently addressed by the dealer, and that's my concern. I dumped those cars, cause frankly, it bothers me a lot.
This isn't a quiet engine, transmission, or AWD system. Especially without an example, the first step in diagnosis is to rule in/out actual engine knock. If it isn't severe, a tank of high octane should make it stop. If it doesn't, then it probably isn't knock but something else.
In hot weather I can get a low RPM noise that is kind of ratchety when getting off an back on the gas in short order at slow speeds when trying to maintain a proper speed (i.e. 25 mph residential zone with hills).
My first through was it's too high pitched and fast for knock, but I fed it a tank of 93 anyway. No difference. Based on issues with other vehicles that sounded kind of similar, I checked heat shielding. The renegade doesn't have all that much rigid heat shielding and I couldn't find a potential culprit. It honestly sounds like a valvetrain that needs adjusting, but only for a moment, and it seems to come form the bottom half of the engine bay on the passenger side.
At this point I assume it has something to do with the transmission or AWD system. It seems to be harmless.
Long story short, noises are easier to diagnose if you post something with audio of the noise.