06 Impala w/3.5 V6 - OLM goes off between 5500 and 5800. I use the OLM and run PP in it. Silverado w/6.6 Duramax - OLM goes off right around 10K. I run Delvac 15w-40 HD Dino and use the OLM. I use AC Delco filters in both. You guys keep shelling out your hard earned dollars to the oil companies with their record profits and I will follow the recommendations of the manual which I have done for years without a single oil related engine problem. As others have stated, the only way to be sure is to run an UOA which I have done for both of my vehicles with good results. The OLM for my applications has been dead on based on the UOA.