As mentioned, I posed this question to New Pig Tech. Here's the reply:
That's a new one for New Pig Tech.
Unfortunately, there isn't a simple answer to the shelf life question. Most lube / body shops will give you a three to five year window for a drum of oil - but there are some things to consider for petroleum-based oils (we're still learning about synthetics):
1. Temperature. If the temperature fluctuates greatly, longevity will decrease.
2. Moisture / condensation. Most oil comes in steel drums. If water gets into the drum, it can cause it to rust. In addition to rust particles getting into the oil, the mix of oil and water can create a breeding ground for bacteria and some really bad smells.
3. Additives. If the oil contains additives, time can cause these to fall out of suspension.
4. Exposure to air. Oxidization can occur when containers are left open. In addition, open containers are a prime cause of leaks and spills. Keeping them closed not only helps with the longevity of oil, but also helps prevent pollution!
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My blog post linking to this discussion is
here.