Uneven temperature reading on CPU, thermal paste not even?

Ok, so this is my first home build and my first time applying thermal paste. I have a Q9550 with an arctic cooler freezer 7 pro and I used arctic silver 5 thermal paste. As I look at my temperatures now (its 1230am and I have my window open) the temps read (at no load) 32, 30, 26, 33. During the day, the temps run around 39, 37, 31, 39 (at no load). I'm just wondering if I didn't evenly apply the thermal paste because no matter how warm the temperatures get, there is always about a 7-8 degree difference between the lowest and the highest temp readings.

So I'm just wondering if I applied the thermal paste wrong/unevenly or if this is normal for four cores.

Thanks in advance.

I think that it is normal. My OC'd Q6600 has a temp differential of about 5 C - 6 C under load. My OC'd Q9550 has a differential of about 4 C. under load. Remember, both of these are not "native" quad cores. They are both made up of two C2D's glued together under one heat spreader.