Pitch or Not?!?!

I'm brewing a double ipa 1 gallon batch with an OG of 1.083. I have a purepitch of WLP001 that is over it's best by date by about 2 months. I was planning on originally pitching half of this, before, but am now thinking about just pitching most (80%+) into what will be a 1.2 gallon fermenter amount.
What do you think?

 

If in doubt, make a starter. 1.083 is pretty big. You want healthy yeast for that. If it was me and the wort was in a lower range like 1.055-1.065 on a 1 gallon batch, I'd just go for it and pitch. But in this case, I would make a starter.

 

How the yeast was stored will determine its viability. If kept refrigerated your yeast that is past it best by date will have nearly the same viability as it had before its best by date.

 

This is not entirely true. Liquid yeast start losing viability as soon as it is packaged. Refrigerating slows the degradation but does not stop it.

Since this is a 1 gallon batch and a fresh pack should be good enough for a 2.5 gallon batch of 1.040. I would not be too worried about pitching as is. I looked at Mrmalty and put in a production date of 8-10-16 and it suggests 1.3 packs. Mrmalty gives a viability of 51%

Making a small starter would give you the healthiest yeast to pitch though.

 

Mr. Malty is a pessimist. Woodland Brewing has different data. http://www.woodlandbrew.com/2012/12/refrigeration-effects-on-yeast-viability.html