How long is too long for a sealed case of GTX 20 40?

[Streetlight Ministry]

I found my lost sealed case of GTX 20/40 about 6 yrs late. Is this oil too old to use?

Can i at least use it to flush out an engine?

 

[NORTY]

You can use it for another coupla years. The key is how it's stored. If it's stored inside a garage where water can't get to it, then you're good.