Zenbook S16 (Core Ultra 7 258V, 32GB RAM) hitting 70-83°C on light tasks (Steam downloads) AFTER a motherboard replacement. Is this normal?

Hi everyone,

I’m a first-time Zenbook S user and I’m honestly pretty shocked by how hot this machine gets. I recently bought a used Zenbook S16 (specifically the Intel Core Ultra 7 258V with 32GB RAM) that is still under official manufacturer warranty. Looking back, I highly suspect the previous owner sold it because of these heat issues.

Right now, my CPU temperatures are constantly fluctuating between 70°C and 83°C when I'm doing non-heavy tasks—like simply downloading a game on Steam.

Here is what I have tried so far:

• Set the fan speed to MAX.
• Updated all drivers and BIOS to the latest versions.

A bit of backstory: I actually just got the laptop back from the Asus warranty center. They completely replaced the mainboard. Before the replacement, the laptop would hit 90°C immediately upon booting up or just watching a YouTube video, which caused massive thermal throttling (the CPU clock speed would tank all the way down to 0.8 GHz).

The current situation: The good news is that the severe thermal throttling and the 0.8 GHz drops are gone since the motherboard swap. The bad news is that the temps still feel uncomfortably high for such light usage, always hovering around that 70-80°C mark. Especially considering this has the new 258V chip which is supposed to be incredibly efficient, this feels wrong.

Since this is my first thin-and-light Zenbook, I wanted to ask:

1. Is this temperature range normal for this specific Zenbook S16 model due to its chassis size?
2. Should I consider this a major red flag and send it back to the warranty center again?

Any insights or advice from other Zenbook users would be hugely appreciated!