So recently my mother gave me a roughly 8 year old riding mower with a briggs 17.5 hp powerbuilt motor. My passed step-dad was not a person to change oil or anything like that, and my mother says she doesn't ever recall him doing it either. So last week I decided to change the oil and do a little maintenance on it and at the end of the oil draining was about 1/4 of a quart of silver metallic oil. The oil was replaced with ST synthetic 5w30 and I've ran it for about an hour since. The mower runs as it should with no weird vibrations or knocks. Checked the oil tonight and found a couple of flakes on the dipstick of metal. Question is should I run some type of flush through it or do 4-5 back to back changes with some delo 15/40 I got for free?