Don't mix RAM voltages.

It will probably cause instability and could damage your system.

Soldered RAM runs at a specific voltage—usually low like 1.2V for DDR4 or 1.1V for DDR5. If you add a stick rated for higher voltage (like 1.35V), the memory controller has to try to run everything at a single voltage. It might work briefly, but you’ll likely get crashes, boot loops, or corrupt data. Over time the extra voltage can degrade the soldered RAM or the controller.

Laptops are especially unforgiving here. They don’t have the same flexibility as desktop motherboards for mixing mismatched voltage sticks.

Just match the specs. It’s not where you save a few bucks.