My MacBook Pro only seems to be using half of the available RAM?

So I've recently purchased a RAM update kit (Crucial 8GB upgrade kit, 1067MHz DDR3) for my Mid-2010 MacBook Pro 13" 2.66GHz. Once the upgrade was made, I started feeling the computer running hotter: fans started kicking in earlier, and iStat Pro is telling me i'm running at around 60 degrees celsius with just Chrome and Mail open, and running in the 70s every time I did something a little bit more intensive.

I've since then been all over the web trying to find out why my MBP would be overheating like this (something I don't think it used to do before) at low CPU loads, and one of the explanations offered was that I might have purchased the wrong frequency of RAM sticks, which later it turned out I hadn't.

Anyway, so I was running a few things today (mainly facetime), at around 72 degrees celsius, after resetting both PRAM and SMC earlier today, and I opened up my activity monitor, only to find that exactly 4GB of the available 8 was free. Is this the sign that somehow one of my RAM sticks isn't functioning, or just a really crazy coincidence?? I checked in system report and both RAM banks have the status OK, so I don't know what to make of this situation at all.

By the way, I swapped out the RAM sticks and my MBP consistently ran 5 degrees C cooler, so I don't think I'm completely delusional about this (as opposed to most people).

If it's of any help, I'm running ML 10.8.2 with everything up to date.

Thanks in advance for the help!

Attached is a screenshot of the activity monitor...

MacBook Pro (13-inch Mid 2010), OS X Mountain Lion (10.8.2)

Posted on Jan 10, 2013 10:24 AM

Jan 15, 2013 9:28 AM in response to Courcoul

yowza! that's a tricky bit of business there, and if in your opinion it doesn't need to be done, i'd rather avoid it ^^ the chance of screwing something up is too big, and not worth taking unless strictly necessary.

i'd love to see adam and jamie take 2 identical macs, scrape the thermal paste off one of them and leave the other intact, and run them.. until one melts dramatically (or some such thing). would be awesome!

anyway, besides high heat-sink temperatures (which doesn't really convince me as a sign of a lack of thermal paste) what are the signs that might indicate a real need for re-application of thermal paste? (if there are such things as real signs, ergo if the problem has actually ever existed).

cheers