I run tap as hot as it goes for fermenter (fermonster), kegs and any bulk/large items.
If something needs a heavier clean, I'll add boiling water and raise the temp closer to 150.
Small parts like poppets, I set my electric tea kettle to 160 and soak in a small pyrex bowl with oxi. Soak until cool enough to handle.
You were so right about 160F.
Yes 160
Does higher than 160F work even better? There's no question that oxyclean works far better at 160F than it does at even 120F.