Is it going to hurt? Probably not.
It is going to help significantly? Progably not.
I presume this would be targeted towards two things:
1) wear reduction
2) HEUI failure avoidance
Why not run some experiments and see for yourself?
First, take a few successive UOAs and find out if your rig is within the typical UOA variation levels; probably is, but you need to check first. Do this while leaving the HPOP buttoned up for the OCIs.
Then run some experiements by siphoning out the HPOP and then taking more samples. To be completely validated and statsitically sound, you'll need 30 OCI samples to develop true averages and sigma levels. Which is why we don't see this done often; most folks don't have the patience and money to do this correctly.
Now - we can look at the huge number of 7.3L PSDs still running fine, and draw some inferences, but not full conclusions. Hence - see my first statements above. Is there conclusive evidence that failures of the HEUI system or excessive engine wear are directly due to not changing oil in the HPOP? Of the units in the field that did fail or have high wear, what conclusive evidence would exist that shows changing the HPOP oil would have saved the engine from that problem? For that matter, we'd have to anaylze if the failure more was directly attributable to the potential shift in volume of "clean" oil now in the HPOP. IOW - because the oil is shared throughout the entire engine, but by differening percent of pressure system, what quanity of failures could either be blamed or pardoned due to HPOP "dirty oil" volume?
When you get right down to it, there is no practical manner to prove such theory, for any common BITOGer. We don't have the money, time, or even variety of vehicles and conditions to prove this one way or another. So it's up to some "bench racing" so-called experts to say yes or no. In that manner, any one opinion is as good (or bad) as another. In short, can anyone who does change their HPOP oil, show conclusive evidence that they reduced wear in a statisically significant manner, or point toward a failure avoided that was otherwise an assurance?
So I stand on my soap box and state this to be emphatically true:
it may or may not help, and even if you experience a failure relating to lube, you'd have no practical way of know if the alternative maintenance program would have saved the failure from happening. We do know that many hundreds of thousands of PSD owners do not change the HPOP oil, and yet see good, long, safe operation.
Do as you see fit.
