Rust caps field of view at 90 and defaults to 70. Those 20 degrees are a real advantage — you see people entering your peripheral vision sooner. The annoying part is that Rust keeps resetting it.
Two ways. In the menu: Options → Graphics → Field of View, drag to 90. Or in the console with F1:
graphics.fov 90Rust rewrites parts of its configuration on major patches, and FOV is one of the values that goes back to default. It also resets if you verify game files or if the config was written while the game was running.
Put it in the config file rather than the console. Close Rust, open cfg/client.cfg in the Rust folder, and add the line:
graphics.fov "90"Save while the game is closed. Keep a copy of the file somewhere outside the Rust folder so you can paste it back after a patch wipes it.
Mostly yes in Rust, but there are two costs. Distant players look slightly smaller, which can make long-range shots marginally harder to line up. And a wider view renders more of the world, so it costs a few frames. For almost everyone the awareness gain wins — 90 is the standard for a reason.
The FOV setting applies to your normal view, not to scoped aiming. Scope zoom is fixed by the attachment, so raising FOV does not change how far you can see through an 8x.
90 degrees. The game does not allow higher, and anything claiming to raise it beyond that is modifying the game — which will get you banned.
Slightly, because more of the world is rendered. Typically a few frames. The awareness advantage is worth far more than that.
Rust resets it on some updates and after verifying files. Writing it into cfg/client.cfg instead of the console makes it stick through most patches.