So if my multimeter is correct my battery must be bad then huh?

I'll stop by NAPA and see, but not for a bit, supposed to get 7 more inches tonight! So much for global warming and living in the "south".

 

https://www.youtube.com/watch?v=Oi8sUE9XCgA#t=31

I noticed the -15 but i didnt see you are in Kentucky thats cold.

 

That is cold for us, I don't care for it any.

Got up to 37* this afternoon so I decided to check again. It was 12.5v. So I cycled the grid heaters without starting and it went down to 12.0v. Turned the key off and it read 12.2v.

 

Coldness increases battery internal resistance. It shouldn't have much effect on open circuit voltage. It raises charging voltage, and depresses discharge voltage.

Coupla thoughts.
1. There's electronics in a digital meter, and that plus moving mechanical parts in an analog meter. I doubt most are made to be run much below freezing, at least with any guaranteed accuracy.

2. This diesel isn't to be expected to start reliably below 0°. (engine heater required). Sometimes they do, and sometimes they don't.

3. I'd get it started, run it till the voltmeter rides where it usually does, then get the battery load tested. That's the only true test of a batteries condition unless you want to analyze each cell.