I was asked by the OP to clarify my recommendation, so I'll do so below and add the rationale for my logic ...
Others may have advice which differs from mine. The OP may have his own priorities as well.
Take the first UOA about 50 miles into the OCI; this will establish the baseline for the oxidation, Si, etc.
Starting out fresh ... change the oil and filter. Use HPL PCEO because it has a robust add pack and is a very cost effective choice. Use any decent filter spec'd for the application; your choice. I'll let you decide what's "best" here.
Take a UOA about 25 to 50 miles into the OCI. This will give Si and Ox values as baseline numbers, so the delta (change) can be calculated from subsequent UOAs.
Then take your UOAs every 5k miles. Build some history for several UOAs.
Every 5k miles, take a UOA.
Don't change the oil unless there's an indication that the change is necessary. Reasons for condemning the oil would be very high wear rates, vis grossly out of spec, Ox way too high, etc. It's very unlikely this will be the case until you get 20k+ miles or more. But the point is to get some data points along the way.
Example ...
- UOA at 5k miles; if all is OK - continue the OCI; change the filter only. If the data looks good, continue. If the oil looks heavily loaded with dirt/sludge (if the soot/insolubles and Ox are really high), you might consider another OCI here. Don't assume an oil change is needed; let the data tell you one way or another.
- UOA at 10k miles; all OK - continue the OCI; again, change the filter only.
- UOA at 15k miles; all OK - continue the OCI; again - filter change.
- etc ...
Change the oil when the data says so, not your gut. The reason for the frequent filter changes is that with so many miles already on the vehicle it's probably going to need a few filter changes to keep the filter from getting plugged up. As the engine gets cleaned through the use of HPL, the need for filter changes will decrease. Make sure to cut the filters open and really look into the media pleats. HPL is such a good cleaning oil that you should not be surprised to see heavy loading of the media in the first couple of filter changes.
Then as the ranges and variations are understood, you can perhaps back off the early UOAs, but not until you have good data
In future OCIs, you may be able to reduce the number of UOAs (costs) by delaying the need for UOAs at the front end of each OCI.
If your UOA history from the first OCI indicates things are doing well, then you might be able to skip the UOAs at 5k and 10k miles, and start the UOAs at 15k miles.
There's no way to know this until you understand the history from the first OCI, as established above.
I am using HPL PCEO in my 2023 ES350 and 2023 MX-5. Because these were bought new, there was no reason to think I needed a 5k or 10k UOA, or frequent filter changes. I plan to take UOAs starting at 15k miles of HPL use. But with used vehicles or those with really high mileage, it's a good idea to do some frequent filter changes due to the unknown loading of "gunk" which will be released by the lube and caught by the filter.
That's my $.02 worth.