Mercedes Benz repair: OIL USEAGE 300SD 1983, vacuum pump, blue oil

Question
THIS HAS NEVER USED OIL TILL NOW, OUT OF THE BLUE,OIL CHANGED EVERY 4000.MILES CASTROL FROM NEW.
3QTS.500 MILES NO SMOKE OR LEAKS I TOUGHT IT WAS THE INJECTORS DELUTING THE OIL, NEW INJECTORS,NO DIFFERENCE,PURHASED REBUILT PUMP.NO DIFFRENCE,TALKED TO A M/B MECHANIC HE SAID TIMING
CHAIN WAS STRECHED.REPLACED IT.NO DIFFRENCE I HAD
ANOTHER TURBO.CHANGED IT.NO DIFFRENCE.HELP

Answer
There is a vacuum pump that supplies vacuum to the brake booster. It has a diaphram that can rupture and draw oil up to the intake. It can burn a lot of oil. Look at the line running from the vacuum pump to the intake and if it is black then it is drawing oil up to the intake.