And a pinch more surfactant(oxy has some), and a chelator. I wrote a long blog post on it, but I'll keep it simple here.
Supplement somewhere between 30-40% of your mixture with sodium metasilicate. It's a much stronger alkali than soda ash + sodium percarbonate(aka oxyclean). A common sodium metasilicate is TSP/90. You'll find it at hardware stores.
Add a tiny, tiny drop of dish soap to your liquid oxyclean + sodium metasilicate mixture after you've mixed with water. That will give you a little more surfactant. More isn't better here, you just need a drop. I've found that works magic compared to oxyclean alone.
What homemade PBW doesn't have is a chelator. Those with hard water know that oxyclean will leave hard water scale on equipment if left to soak too long. My water is Jesus Christ hard (450-490ppm TDS), and if I leave an oxyclean solution overnight, I will have scale in the morning. Chelators fix that. Unfortunately I have not experimented with any yet.
Or just buy PBW.