Thanks very much Sam V/Lubedude. Your answers are so straight & easily understood. I've never exceeded 3000 miles between oil changes, change the filter every time, stayed with the same (petroleum) oil, & tavel far enough to work to reach full temperature for a while. I switched to Mobil 1 at the recommended 5w-30 viscosity just today, & cleaned out all the white stuff in the fill tube & baffle. I am a big proponent of never turning the engine off until it has at least reached full temperature, especially living here in New Hampshire, so running short trips is not the problem. Thanks for your help. I'll advise if I experience anything different with the synthetic oil.