Many thanks for the oil analysis. You were right about the spike in silicon! Yes, the poor air filter had suffered a backfire during the engine start. The backfire evidently occurred since the last oil change. The heat warped the air filter, allowing dirt in and depositing goo in the air duct. We just got a new air filter and cleaned up the air duct during annual inspection. I’m not sure what I did to cause the backfire. First time in 30 years of owning the plane that I’ve done that. Anyway, thanks again – your detective work was spot on! Love your newsletters and archive articles. Have a great holiday season!