It depends on how much oxy. You would feel pretty damn good off 50mg of demerol, having no tolerance, even with I was great. 20-30mg of oxy might, straight, put your head in the toilet for a while(opiate virgins). Demerol is very euphoric for me and I am very coordinated in every way while on it.
Once, I ripped the 50mg demerol 3 hours post of an oral dose of 40mg of hc tussive. I felt 'perfect'. Not sleepy, wired, or brain dead, just pure fucking bliss!!!
If I plan on doing demerol in the future, I would take it orally. I've only snorted two opiates, demerol and oxy(2 times and ~6 times), so I don't have much experience with other methods of delivery. I'm satisfied with oral use.