There’s plenty of clean-running engines, robust oils and high-efficiency, high holding capacity filters that can easily exceed 12k miles without risk or excessive wear of the engine.“Best” is a filter that is changed at a reasonable interval. Not 12k miles….for any oil or filter. That’s how you can absolutely ensure your engine has clean safe oil.
Just one example, I had a FE10575 that was in service for nearly 23,600 miles. I had UOAs done at ~7500 & ~22k filter-use miles that showed low insolubles and wear rates below the average for the engine family. The 7500 mile sample was at the end of a 15k OCI where I changed the filter mid-OCI, and the 22k sample was an in-service sample taken at 14.4k on the oil which was then run to 16.2k total, when both the oil and filter were changed.
I don’t recommend blindly jumping from 3-5k OCIs up to 15-20k, but there is little-to-no risk when using the method @wwillson has thoroughly documented, which enabled him to go ~34k on a single OCI (with a couple filters & top-up oil).
Statistically speaking, over the life of the engine & vehicle, there will likely be no reduction in service life by using long-drain oils & high-capacity filters to their maximum safe life verified by UOAs vs using these oils & filters but blindly changing them at set mileages (like 3k, 5k, 10k). A UOA’s true purpose is to tell you when the oil isn’t serviceable, or when your filter has been loaded enough it’s allowing insolubles to circulate at concerning levels. @dnewton3 has repeatedly posted data gained from large fleet UOAs that prove without a doubt that even using conventional oils and filters which prove there are very minimal risks to extended UOAs on many engine families. In some cases the conventionals were shown to go well over 10k before the oil was condemned or began to cause increased wear metal accumulation.
Therefore, the only real effects of fixed, short mileage, “blind” OCIs result in increased oil & filter waste, increased costs, and increased service downtime. None of those are “wins” IMO vs no statistically significant increase in engine service life. TL;DR: You’re going to sell or wreck the vehicle long before engines fail on modern oils and filters, whether you change the oil at 5k or when the UOA says it’s wise to drain the oil. The longer way saves you time and money once you’ve established the safe maximum for an oil/filter combo
