Are you talking about Frantz bypass filter that uses toilet paper roll as the filtering medium? If so, what OCI do you plan to use? I have installed a Frantz oil bypass filter on my 2003 Toyota Echo, and ran a 30k miles OCI with TP change every 3-4k miles with 1 qt of makeup oil. I use M1 5W30 exclusively since engine was new. The end result was not very satisfactory. The used oil was very dirty and a bit thick even though there was no evidence of sludge.
After the full oil drain with a fresh TP roll installed the oil in my engine now looks brand new after 1500 miles of drivng. I am thinking of doing next oil change around 5k. I will not try another 30k OCI again, but, use the bypass filter as a supplement to ensure a safe and long OCI with clean running oil all the time.
With a V8 engine the 3k TP change interval in the long run is too long in my opinion. Maybe even 2k is too long if you do a 30k OCI. It all depends on your OCI. Some members said the TP is still good as long as the canister is still hot to touch which means good oil flow (TP not yet plugged up). When I replaced the used TP at 3k mile interval, the canister still felt very hot; but, I thought I had to replace it in order to put makeup oil because the oil in the engine was dark. Actually replacement of TP and partial oil change with makeup oil can be performed separately.
This is what I would suggest. I would install a Fumoto oil drain valve to your oil pan if you have not done so. It comes in very handy when it comes to do a partial oil drain. When you think the oil is too dirty, then drain a quart of used oil with a measuring cup, and add a quart of makeup oil if the canister still feels very hot. Your used oil in your engine will look brand new after driving for few miles to let the TP filter it. Make sure you touch the canister when the engine is fully warmed up. If the TP needs to be replaced, then replace it and add 1 quart of makeup oil (you might need to drain 1/2 quart of used oil prior adding the 1 quart makeup oil if the oil inside the canister drained back into the engine when it stops). It is all about partial oil change that does not necessarily involves the replacement of TP everytime.
