If you got this far, don't blame me if you don't like the challenge. I spelled it all out in the subject line. This is really a poll because I'm curious. What are people's experiences with extended OCIs (more than the typical manufacturers' advice of 7,500 miles under "normal service") <i>vis-a-vis</i> engine longevity. I'd appreciate honest responses of the intervals and what, if any, engine mechanical malfunctions that might conceivably have been attributed to the oil, and at what point in the engine's life they occured.