From everything I read and been told by professionals, Synthetic opiods like oxy typically are untraceable by 2.5 days. Mind you this depends on how heavy you've used. One of my acquaintances who actually does these test told me that synthetic opiods are pretty much undetectable after 4 days even if you were a heavy user. Oxy has a VERY short half-life and is not fat soluble like cannabis. If it;s been longer than 4 days, don't think twice about it.
However, you may want to seriously consider the impact of using drugs illegally. I never have myself nor would I ever. Even at the height of my dependency, it was all legal.
That my friend is the difference between W/D at home or in jail.