motor has 250000 kms on it - mostly highway (roughly 150000 miles). anyways ran great until oil light flickered at idle and then got a bottom end knock. pulled.... rods fine mains chewed. replaced main and rod bearings (crank polished and everything plastigauged) . after a few thousand miles i think my knock is returning. question is - i've noticed at idle there is no noticable oil on the dipstick, engine off level is fine. there is oil dripping from the return line on the side of the pan when loose and engine running. oil light is off. how can i determine if there is nothing blocking the oil lines for sure and what would be eating my mains?