I'll tell you though, when Im sick/WD- I would take 25mg of methadone over 80mg of oxycodone anyday. But, yeah; analgesic effect and euphoria are definitely different concepts.
As far as taking too strong a dose, I think having someone else present, especially if they know cpr and how to administer narcan, is one of most important things to do. Especially when trying something new, or doing a higher than normal dose.
(Not that I'm condoning taking as big a dose as you want cause you can be resuscitated. Just saying from a HR view, having a second person on hand is important.)
80mg of oxycodone ER isn't likely to OD anyone who has even a little bit of tolerance, but that doesn't mean it will be enjoyable. From experience, taking more than needed to get off, but not enough to OD you is not just dangerous but extremely uncomfortable. That's why when some people try opiates for the first time, they have a poor experience cause they took more than necessary and ended up puking all nite with a headache. I never tell them that tho, cause that's usually the last time they do it. Easiest way to make someone who's never done opiates to stay off of opiates forever is give them a 8mg suboxone.... after the 4th time they puke they'll never want to touch them again.