Backround: 1997 Toyota 4Runner 3.4L 215k miles Last oil used- Napa synthetic 5w-30 with Toyota oil filter Oil in serivice- 5,886 miles I did an oil change last weekend and towards the end of the oil drain, the sound of the oil draining changed and the oil seemed thicker and had what looked to be metallic shavings were in the oil. Instead of filling with fresh Napa synthetic again, I went and bought some Walmart Supertech oil and filter to try and flush the engine. My question is how long should I run this oil in order to get a good sample to send off to Blackstone? My initial thoughts were to run it 500 miles, change it, sample it and put some fresh synthetic back in and run another 5,000 miles and sample again. Any help or thoughts would be appreciated.