7V or 12V only a 1C difference?

[Dutch Guy]

Yesterday was (finally) a warmer day so I could do some testing with my new system.

The CPU temp is normally 36C but as the ambient temp was 25C instead of 20C the CPU temp was a little higher at 39C

I run the 120mm fan on my rad at 7V but last night thought I would see what the difference was at 12V (besides the noise) and was surprised to see that it only made a 1C difference

So what does this mean, my rad is too small, my fan is underpowered or the sensor is crap?

 

[Dutch Guy]

CPU: San Diego 3700+ @ 2750Mhz 1.525V

Radiator: Aluminium heatercore 120mm:

Waterblock: Innovatek rev3:

Maybe the small diameter tubing (8mm inner, 10mm outer) stops me from getting better performance?
Or maybe the radiator can't get rid of more heat due to the limited surface area?

[edit]saw your reply, looks like you get a smal difference as well, strange that this wasn't noticed by me in the past as I had watercooling for years now [/edit]