Well, methadone is certainly a very sedating opioid with a fairly high side-effect profile. It is fully synthetic, which can lead to more of a different opioid high. What you must remember with methadone is that it takes a very long time to peak in comparison with other opioids or any other drugs, really, and so re-dosing too soon can be very dangerous. I don't have any personal experience with methadone, but I would certainly exercise caution upon trying it. Even though you have some oxycodone tolerance, you might not be as tolerant to an equipotent dose of methadone, so I would start with a rather low dose. Again, it is more sedating and noddy than oxycodone would be. I would wait until the oxycodone has worn off subjectively (until you can't feel the oxycodone anymore), and then try a very low dose. I'd start with just 2.5 mg methadone to be on the side of caution, and wait several hours before re-dosing if you feel the need, only then re-dose with another very low dose. Methadone will exert effect for a very long while, hence why dosing once a day can be effective for those on MMT, so be extraordinarily cautious about taking the next dose.