I am using Valvolene Dura Blend 20/50 with the smaller filter. 6 months have passed with 2700 miles since I last changed the oil. I don't remember seeing this powdery residue coating the two magnetic strips.
contact Blackstone labs in Ft Wayne IN, they'll send you an oil sample kit for free. Mail them a sample of your oil and they'll tell you exactly what's going on in that engine. I've used them for years, first with my airplane then with my Alfas. Their expertise is well worth the $25 price of an analysis. About Us