Thanks muchly for the advice,
I will tell my Dad to just send the used Mobil 1 that he was saving for me to the recycler,, I was afraid there might be a situation like the higher boiling point of the synthetic oil making it bad for a quench oil,, I hadn't even thought of the detergents and other additives in it.
As for the safety issues, I'm damn near 50 now and have been a machinist all of my working life,, I've been called a " saftey fanatic " by more than one person before,, but then I still have my eyesight, hearing, and all of my fingers,, if it takes being a fanatic to keep it that way, so be it.
thanks again, Bear