Can i take suboxone 8 hours after taking oxycodone?

That depends on whether you are taking the morphine recreationally (to get high), or if you are taking it for pain.

If you are taking it to get high, then no, it won't work. You will have to wait at least 36 hours, but probably more like 48 to 72 hours, until the Suboxone is out of your system, before you can feel the effects of the morphine.

If you are taking it for pain, then yes, it should still work as a painkiller, even though it won't get you high.