I've got an old can of Pentosin CHF 202 and a basically dry reservoir. On the can, there's a date, preceded by the word "Verfall." Knowing the answer already, checked GoogleTranslate and, of course, it means "Expiration."
The date? 1/2015. It's pretty much a full liter, so I poured maybe a shot glass worth out onto a rag. I know this probably means nothing, but it looks fine. Clear, green, just the way it did last time I topped things off.
Obvious question: does this stuff actually go bad? If so, would it be bad to use it to top off until I get around to getting some more? (I'm just itchin' to go for the first drive of the season
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