[SOLVED] Thermal paste

It depends on if the cooler/sink/water block you purchased already has any applied or not...

If a naked cooler with nothing pre-applied for thermal conductivity, then....yes, you do. (Unless using one of the newer graphite pads, which, per Linus Tech TIps' testing, works quite well!)

Every cooler need something to help it properly mate (thermally) with the CPU's integrated heat spreader....