On Wednesday, October 10, 2012 3:51:16 PM UTC-7, Cydrome Leader wrote:
Phil Hobbs wrote:

The part I've not figured out is why or how does silicone diffusion pump
oil go bad, and why does it have an expiration date on the bottle.

Probably because some silicones are used in medical devices, and
the FDA gets very crazy when they cannot determine expiration
dates. Or calibration dates.

It also means some customers will reorder more often. I recall,
however, we loaded our diffusion pump and NEVER thought
of replacement of the silicone oil unless it got too dirty to pump.