Don't mix RAM speeds if you can help it.

You can, but your system will run everything at the speed of the slowest stick — including your existing 16GB kit.

That means your original RAM gets kneecapped to match whatever new stick you throw in. Timings follow the same rule: everything synced to the loosest timings in the mix. You might also run into instability if the sticks don’t like each other. It’s not guaranteed to crash, but it’s not a gamble worth taking for the few bucks you save.

If you want 32GB total, buy a matched pair and sell your old kit. Or buy an identical stick to yours (same model, revision, and batch if possible). Otherwise you’re leaving performance on the table that you already paid for.

Future you will thank you for spending the extra few bucks on a matching pair.