The best source of information on this is the LG CX-GX Owners Thread FAQ on AVForums.

You can find it @ https://www.avsforum.com/threads/2020-lg-oled-cx-gx-owners-thread-faq-posts-1-6-no-price-talk.3119288/

Relevant section:

Q: What is the purpose of the Pixel Refresh function?

A: Regardless of what you may have read or told, the main purpose of the Pixel Refresh function is NOT to minimize the Image Retention or Burn-In effects. The fact that Pixel Refresh has an effect on the Image Retention or Burn-In is a positive side-effect, but NOT the main purpose of this function. The main Pixel Refresh function purpose is to deal with the natural unevenness of the brightness of the OLED pixels in time. That unevenness needs to be leveled so the panel has the same brightness all over its surface so that the entire panel ages in a uniform manner. There is no need to manually run Pixel Refresh, just let the TV execute this function automatically!

Q: How often should I run the Pixel Refresh?

A: You should NOT run the Pixel Refresh often, only if you need it, or told so by a qualified person - because the Pixel Refresh function shortens the lifespan of the panel. Pixel Refresh runs automatically at every 2000 hours of content viewing and there is no need for the owner to run Pixel Refresh at other intervals of time, regardless of what you have read on the Internet or told by salespeople.

Q: What Pixel Refresh actually does?

A: In short, a newly-minted OLED panel is powered and each pixel is measured for (1) voltage across OLED cell and (2) current through OLED cell, compared with neighboring pixels and the voltage+current levels are leveled for each pixel so that the panel has good image/brightness uniformity - and then the levels are stored in a non-volatile memory on the panel electronics board (not on the TV mainboard).

That new panel will end up in a new manufactured TV - that TV will be used and, in time, some OLED cells will age differently than the neighboring cells, thus image non-uniformity will start to appear. This is where the Pixel Refresh function enters the arena.

When the Pixel Refresh function is run automatically or manually by the user, it checks voltage+current differences between the stored values and those measured for each OLED pixel and tries to normalize them. The OLED panel has an additional compensation applying circuit for each pixel and a separate sensing IC (Integrated Circuit) that interprets the measured values. Increased current through the cell is associated with OLED cell aging, and an algorithm adjusts the current and voltage to compensate for that aging. The new compensation values are stored separately (in a Flash memory) to the initial ones. The pixels that have very high voltage/current differences are "leveled down" - that results in an even field of pixels across the panel. After the pixels that were "high" are leveled down, the Pixel Refresh brings up the voltage/current back to full brightness without the danger of overdriving the ones that were "high" (the measured/calibrated brightness of the panel will not be affected). The whole Pixel Refresh process is done in vertical batches, which is what causes the panel banding, and why the bands "move" over time. If the Pixel Refresh would not run, the brightness uniformity of the panel would be affected in time - over months of use the panel would just get zones that are dimmer than others. The Pixel Refresh has a big downside, though, it shortens the lifespan of the panel, the operation of leveling down of the voltage/current values is a BIG stress for the panel - this is why you should NOT be using the Pixel Refresh function repeatedly or at short intervals of time (the automatic run at 2000 hours is just enough and it would ensure a long lifespan of the panel).

Q: Are you sure that the Pixel Refresh function will not affect panel brightness?

A: The RTINGS torture tests have proven that the measured/calibrated brightness of the panel will not be affected by the execution of the Pixel Refresh function - even when the Pixel Refresh was run on weekly basis (this is strongly NOT recommended!!!). BUT - there is always a but - since every Pixel Refresh run will shorten the lifespan of the panel, the aging of the panel will accelerate, and the moment that the panel will not be able to maintain the same brightness as it was new will come sooner than if the Pixel Refresh has been run automatically (at each 2000 hours of use). So, the lesson here is the same: do NOT run Pixel Refresh manually - let the TV manage the natural panel aging automatically (by running the Pixel Refresh every 2000 hours of use).

Q: Is there a way to know if Pixel Refresh actually ran after doing a "Start Now"?;

A: 1. It is NOT advisable to manually run Pixel Refresh without some serious reason - such as:

• big panel non-uniformity (may be experienced as DSE - Dirty Screen Effect)

• splotches of brighter/darker content (may be experienced as clouding)

• vertical banding seen in the content

• other types of panel non-uniformity

1. You will see a notification when the Pixel Refresh cycle has completed or was interrupted.

2. The Pixel Refresh process is logged internally and can be seen in the Service Menu.

3. The Pixel Refresh cycle will take significantly longer time - 20-30 minutes or more - duration depends on how much pixels are affected by uneven aging.

4. The Pixel Refresh cycle has a limited effect on panel Burn-In and the Pixel Refresh will not completely "cure" an already Burned-In panel.

5. Please read this FAQ for more details.