There is no "standard ratio" & there is absolutely no reason to mix the powders. If someone has a tolerance to either oxycodone or coke they will need a whole lot more of that drug to get high. This could easily lead to overdosing on the other drug. Even without tolerance people vary widely as to their reaction to drugs. Personally, I think adding cociane to OC would ruin it, and I'm sure others would think the OC would ruin the coke. Just keep them separate.