Electronics question

[MonzaRacer]

Ok, for the first fun fact you dont switch to synthetic to get longer oil changes, period.
With a synthetic you should switch to it to give extra protection under stress and the ability to use tighter clearances,thinner oil for less resistance to motion/economy.
It by no means lets you double your mileage between changes. If you were told that then you listen to someone still stuck in the AMSOIL 80's.
I can tell you for the fact you may take a oil change from say 3000-3500 to 4000-4500, but it does not let you get away with 7500-15000 mi oil changes.
I use synthetic for multiple reasons and one is Ican stretch a change a few extra(say for one pay period) days. Not months or thousands of miles.
As an engine builder please dont get fed hype on change mileage advantages as there are few.
Additives are depleted expotentially as the oil ages.
AS for the reason for changing filters say mid change,,,no no, no. If its worth changing filters change oil.
If you really want to manage your oil install an hour meter on the negine and watch your hours per week driven, and per oil change. Do a few analysis on the oil and plan a little. Donthink synthetic makes your oil bullet proof,,, it doesnt.
But good luck if you want o mess with a system that wont help maintain your engine any better than just pullingthe plug and screwing on 2 new filters.
Now if your say 2000 into a 3500 mi oil change and want to autocross, check the condidition ofthe oil(color) and maybe swap filters for a cheap mental pat on the back, BUT if I wasgonna do it $25-$30 in oil and what $10 in filters before a race/etc would be cheap.
Besides I have NEVER seen an engine lost because the filter bypassed, failed yes but more are due to oil break down due to lack of changing (ie all oils "wear out" some are just better out of the bottle) or a filter failure in the outer casing.
The setup your thinking about wouldrequire many thousand miles of experimenting AND monitoring ,preferably by electronic means.
See to do this you would have to have oil temp bias figured, differences in your connections(ie pressure/flow loss on each side) engine temp bias figured, type of miles driven (ie engine speed).
you would also need a way to qualify both filters before doing so.
My question is, have you ever had an engine fai ldue to filtering?
If no this is a waste of time/resources and simply change your oil at say 4000 vs 3000 or 4000 vs 5000.
Besides being of a very limited benefit its just not gonna protect like a regular change schedule.
Trust me I switched to sythetics al ong time ago and only use extended change times if I have to wait to buy the oil/filter no more.
Good luck what ever you do.