Is there Brown-out detection for Arduino Uno?

[JChristensen]

The brown-out detector can be set for 1.8, 2.7 or 4.3V via the extended fuse byte. Arduino Unos are set for the 2.7V level. I'm currently working on a project where it was beneficial to change it to 4.3V.

Isn't 2.7V a bit low? At 16 MHz the processor requires 3.78V. So it would become unreliable before the brown-out reset kicked in.

Agree completely, but it is what it is!