1996 Infinity G20 When I first got the car it did not knock as much as it does now

What is the octane rating of the gas that you put in the car. The octane rating it very important, here is why; many people do not know what octane is or how it works. Octane is an additive oil companies put in gasoline. Gasoline is very explosive, and when you compress it, it spontaneously explodes. Octane simply put, prevents this spontaneous explosion. The higher the octane level, the less spontaneous explosion. Why is this important? When your piston, inside of your engine, is coming up to the top of the cylinder, it is compressing the gas/air mixture. If this mixture explodes as the piston is on the way up, before the spark plug ignites it, this causes what we describe as fuel ping or a knock. This also will cause severe damage to the engine in time. Run your tank down to almost empty and try a higher octane fuel. If this doesn't do the trick let me know and we will take it from there.