Help with an outside electrical plug

[JamieJackson]

Can someone tell me what this is for?

[musigenesis]

It's the connection for your block heater. It keeps your engine warm so it's easier to start in cold weather.

[Brad_SwiftFur]

As noted, block heater plug. I'd plug it in for temps under ~32, but only if you plan to start the engine the next day, no need to waste power if you're not going to need to start the engine. Typically takes about 3-4 hours from stone cold to pre-heated engine.