Pinging is the term for the fuel being ignited just a smidgen early (Timing too advanced)...

Imagine pushing a kid on a swing...the piston is the kid...

Essentially, the piston is heading back to get another push...but we start the push before he's completely finished coming towards us, jolting him a bit. (Pinging him)

If we have the right timing, we push just after the kid reaches the apex of the swing to us, and is just starting to swing away again, so we get a smooth transition of momentum. (No ping, happy kid...)

If we push the kid when he is coming to us, but not even slowed down enough yet, we can knock him right off the swing....that's knock, a more severe ping.

Octane just describes the speed of the flame propagation, think of it as how fast the fuel burns...the higher the octane, the slower the burn.

Higher octane burns more slowly, so it needs the spark to be delivered a bit sooner to give it time to burn all the fuel, and give the kid (Piston) a good long hard push....

If you use a lower octane fuel than your timing is set for, it burns more quickly, and pushes a bit early, essentially advancing your timing...and that of course can produce ping....or, in extreme cases, knock.

X's tuned for regular on the other hand, if you put hi-test in them, just blow extra hydrocarbons/unburned gas out, and start their push too late in the cycle.

Modern engines have a knock sensor system, and when they detect knock, they back off the timing until its gone...but keep it right up against the limit if they can.

So - if your engine calls for premium, you get better performance with premium....and your knock sensor will back off the tiing to prevent damage if you use lower octane than its designed for.

If your engine calls for regular, you get better performance with regular....and no benefit from premium unless you change the engine timing, etc.

There are exceptions, such as if your engine is out of tune, you can correct for the wrong timing by using the wrong gas to compensate...and at high altitude, you need lower octane or you lose power in the mountains....and in death valley, etc....you may need higher than normal octane, etc.

So - if you are watching for ping...so is your knock sensor....and it likes just a tiny tiny hint of ping to feel secure.