case drain through second aux circuit?

Many small excavators are equipped with a second (medium pressure) aux circuit which has its own pump. Can this serve as a case drain? I think it depends whether the medium pressure system has its own filter. Can anyone say? I'd be curious to know this for a Cat 312, Doosan DX140, and a Komatsu PC138. (Assume recent versions of each.)

For the curious, here is the backstory: A while ago I floated the idea of leasing an excavator to use with an attachment that required a case drain. All...

case drain through second aux circuit?

case drain through second aux circuit?