I DID CHECK THE OIL PRESSURE GAUGE, AGAINST ANOTHER GAUGE, NO CHANGE. I HAVE TRIED 20 W 5O SYNTHETIC TO 30 WT ROTELLA T. STILL NO CHANGE. I DID TALK TO A MERCEDES MECHANIC, HE IS CONFUSED, AND HE DID SAY IT WAS NORMAL FOR A DIESEL TO USE 1/2 QUART TO 1 QUART OF OIL PER 3K.