One can burn avgas in a PT6 but there is a limit on how long for, and an inspection is required afterwards - IIRC. I recall a figure of 50hrs max.
I reckon the avgas will be just fine, but as stated I would use it in one wing and not the other
Also, there are testing facilities available, which might be a vast factor cheaper than disposing of it, and if it tests fine then you can fly on it in the knowledge it is OK.