Well, here's how different interface materials rate. The test setup was the same as during the cooler test. To maximize the stress on the interface material, a very good heatsink was used, the Dynatron DC1206BM-O.

The thermal greases used were different brands of either zinc-oxyde / silicone based or silver based grease (Artic Silver II in this case).

For the family of phase change heat transfer pads, a chomerics pad was used. Whenever you see a pink pad, chances are good this is a chomerics pad. Other manufacturers are Bergquist (black) or Dow Corning (black).

"Phase Change" refers to the behaviour of these pads. While their consistence is gooey at room temperature, they get liquid if heated over a certain limit (somewhere over 50°C).

In general, these heat transfer pads are not inferior to generic zinc-oxyde greases in terms of performance. To the contrary, according to experts they keep stable for a longer time than grease. The downside of using these pads is, however, that they can be used only one time. After that they have to be carefully removed and a new one has to be applied.

A few tips for removing heat transfer materials, as this was frequently asked in the forum :

Grease
Use a cloth or tissue paper to remove as much grease as possible. Then use another cloth dipped in alcohole (maybe known to you as rubbing alcohole or denaturated spirits) to clean the CPU or heatsink.

Chomerics Pads (Pink)
Whenever you encounter those, a little more work is needed. First of all, remove as much as you can from the sides of the CPU die using a soft stick such as wood or plastic. Place the heatsink on a table and pour some alcohole over the pink pad sticking to the surface, just enough to make it wet. Alcohole does not really solve the pad, but when you now use a credit card to scrape of the goo, the alcohole makes the job easier by causing the scraped off parts to be less sticky. Scrape off as much as you can. Now use acetone on a cloth to clean the rest off the hetsink.

Other Pads (Black)
Use a credit cards to scrape off as much of the black pad as possible. Now use alcohole on a cloth to clean off the rest.

Now for the results :

(all values are °C, lower is better)

Not much surprise is that with no heat transfer material used (Air) even the best cooler has a hard time to get the CPU down to a reasonable temperature.

A little more surprising is that the "standard" white zinc-oxyde thermal grease can be of quite different qualities. I know of only few shops which will tell you what brand of grease you buy, so there's some luck involved if you get a good or not so good grease.

On the other end of the scale is silver based grease. This is a lot more expensive than the simple white grease, but, as the results show, has very good heat conduction characteristics. Wether the different brands of silver based grease are of different qualities, too, has still to be tested ...