I've used 10/30 since new. Mostly Penzoil, but have used other brands occasionally, but always 10/30. I used to use Fram or other brands, but have not used those in many years. I purchase NAPA filters now. Oil changes were done from 3000 to 5000 miles. In 33 years, I have done all the changes.
I followed the directions on the SF label - 6 oz. in the oil BEFORE changing. Run it for approx. 1000 mile, then change. It seams odd to put the SF/MMO in with dirty oil. Would it be better to put it in a fresh change. Run it for a 1000 miles then change again?