Does Mayonnaise Last as a Thermal Compound?
By Rafael Coelho on June 28, 2013
Back in 2011, we tested mayonnaise as a thermal interface between the CPU and the base of the cooler. Amazingly, it worked nicely, proving to be, at least in a short term, a better thermal compound than several well-known commercial products. But, at the time, we could not determine how long it would continue to work before a degradation in performance was noted. This time around, we ran a long-term test to determine if mayonnaise can last as a thermal compound.
We applied Hellman’s (known as “Best Foods” in the West Coast of the United States) “real mayonnaise” on our CPU, as shown in Figure 1.
Then, we kept our system running for 12 days, 24 hours per day, and collected data every day. Let’s see the results in the next pages.
We tested mayonnaise as a thermal compound on a Core i5-2500K CPU (quad-core, 3.3 GHz), which is a socket LGA1155 processor with a 95 W TDP (Thermal Design Power). In order to get higher thermal dissipation, we overclocked it to 4.0 GHz (100 MHz base clock and x40 multiplier), with 1.3 V core voltage (Vcore). The cooler used was the Cooler Master Seidon 120XL, which we reviewed recently.
We measured the core temperature with the CPU under full load. In order to get 100% CPU usage in all cores, we ran Prime 95 25.11 with the “In-place Large FFTs” option. (In this version, the software uses all available threads.)
Room temperature measurements were taken with a digital thermometer. The core temperature was read with the SpeedFan program (available from the CPU thermal sensors), using an arithmetic average of the core temperature readings. During the tests, the panels of the computer case were closed.
We calculated the Delta-T (difference between the core temperature and room temperature) immediately after starting the test, at four hours, and at eight hours, and after that, we repeated the test once per day for 12 days.
Between the tests, the system was working continuously, running the Folding@Home SMP client, in order to keep the CPU warm and stressed.
Operating System Configuration
We adopted a 2°C error margin, meaning temperature differences below 2°C were considered irrelevant.
We tested the temperature once a day for 12 days. The results of those measurements are shown in the table below.
|Time||Room Temp.||Core Temp.||Temp. Diff.|
|0 h||12 °C||53 °C||41 °C|
|4 h||16 °C||57 °C||41 °C|
|8 h||15 °C||56 °C||41 °C|
|24 h||12 °C||52 °C||40 °C|
|2 d||13 °C||56 °C||43 °C|
|3 d||15 °C||61 °C||46 °C|
|4 d||14 °C||60 °C||46 °C|
|5 d||15 °C||62 °C||47 °C|
|6 d||14 °C||61 °C||47 °C|
|7 d||14 °C||61 °C||47 °C|
|8 d||13 °C||61 °C||48 °C|
|9 d||12 °C||60 °C||48 °C|
|10 d||14 °C||61 °C||47 °C|
|12 d||12 °C||59 °C||47 °C|
In the following graph, you can see the evolution of the temperature differences over time.
The collected data is very self-consistent, because even with variations in the room temperature, the temperature difference didn’t vary in an unexpected way. When the temperature was reduced, the variation was below the error margin.
The thermal performance was constant in the first two days of the test. At the third day, the performance began to degrade, stabilizing after the fourth day.
Figures 2 and 3 show the CPU and the base of the cooler after the 12-day test. It looks like the copper at the base of the cooler was somewhat oxidized. We managed to clean both surfaces, but it took a soaped sponge to do that.
Let’s try to answer the question we initially posed. The answer could be “not very well.” The initial performance of the mayonnaise nearly equals the performance of good “real” thermal compounds, and lasts for about 24 hours.
After that, the cooling performance degrades. But the temperature difference stabilizes at about six degrees Celsius hotter than the initial temperature, which is not a complete disaster, but obviously places mayonnaise below the performance of commercial thermal pastes.
So, does mayonnaise last as a good thermal compound? No, it doesn’t. But does it stop working as a thermal compound? Absolutely not. After a couple of days, it works as a pretty poor thermal compound, which is better than no thermal compound at all.
Also, after 12 days the metallic cap of the CPU and the base of the CPU cooler were pretty oxidized. Even though we could remove this oxidation with a sponge, we don’t know what would happen after a longer period of time.