My 2006 Honda has an OLM. If all vehicles had this there would be few debates here about OCI - just change oil when the OLM shows an oil life expectancy of between 15%-0%. This is what my Honda manual says and there is no mention of mileage or severe/normal conditions use because the maintenance minder shortens the oil life expectancy assumption for things like cold starts, engine temps for short trips, heavy engine loads, and a few other things. In other words, it sort of penalizes the oil for certain conditions that it monitors and is reflected in the percentage of oil life expectancy it displays.
This thing is not fool proof of course but it has a proven track record at Honda and an even longer one at GM, the developer of this contraption. Tests have shown an OLM is pretty darn accurate and sure makes more sense than going by some arbitrary figure like X number of months or X number of miles; that kind of thinking started 100 years ago. Also, these things are usually calibrated for dino so synthetic use should give even greater leeway as to OCI.
Just go by the OLM, change to the weight oil the manufacturer suggests, use name brand oil such as Havoline, Chevron, Superflo, MC, whatever, and sleep well. If you still don't trust it, use synthetic or go with LC20, FP60 and get a UOA to tell you if the OLM is telling you the truth or not.