I've got an Isuzu 97 kb 250 van that I converted to a 2.8 turbocharge. It started having oil leaks and it was smoking. It also gave me oil warnings as the light would flicker time to time. I then had to overhaul my engine. I put in new sleeves, new rings and bearings. New crankshaft and bearings, new big ends, new camshaft and bushes, new oil pump. I then put castrol diesel oil 15w40.
*sidenote* I even had my injectors serviced and diesel pump done at bosch.
The car started perfectly, ran smoothly and all but that only lasted for about a week. I then noticed the oil light was on. And apparently my oil was not pumping.