Mate. Engine Ping aka knock will lead to more serious and costly engine damage. Are you sure your car is not meant to run on premium fuels only? If you find it runs fine on premium then i'd say that's what it is. (this is usually written inside the fuel flap) alternatively, if you find that the car specs say it can run on normal unleaded, then I'd say you have a detonation problem. the reason you are hearing it more when going uphill is because of engine load. This can be due to ignition timing - You'll need to retard it to solve detonation. You can adjust this by turning the distributor (I forgot which direction - it's been a while). You'll need a timing gun to do this properly. timing is expressed in "degrees before top-dead-center" or BTDC. You'll need to consult other resources to figure out what is the proper setting. If you don't have a timing gun, you can buy them for fairly cheap. My recommendation is to take it to the mechanic if you're not too confident. But do it ASAP or you'll stuff your engine up.