Hey fellas, new here with a few questions if you can help. 1. Does only the toyota oil filter have the anti drain back valve in it to keep the timing chain taught for no rattle start ups? 2. At 100,000 miles can we run straight grade 30 wt chevron oil in it to get the pressure up a bit? 3. If the origin of the motor is unknown, what can we look for when removing the valve cover to inspect for timing chain stretch? Thanks for the replys fellas as I am confident you guys know all!! Tim