Truck Repair: OIL CONSUMPTION, air tanks, oil consumption

Question
FIRST LET ME SAY THANKS FOR PROVIDING THIS SERVICE. I HAVE A 1992 L-10 CUMMINS IN A L9000 FORD WITH A HT750 AL TRANNY. THE TRUCK USES ABOUT 3 GALS OF OIL EVERY 100 MILES AND STEADILY GETTING WORSE. I DO HAVE WHITE SMOKE THAT SMELLS OF FUEL AND A MISS ON WARM UP. ONCE WARMED UP HARDLY NO SMOKE BUT STILL HAVE SLIGHT MISS.MY ? IS COULD A BAD INJECTOR CAUSE THIS MUCH OIL BURN? THEY OUR MECH INJECTORS, HAD VALVE COVER OFF AND ADJUSTED THE VALVES.CAN'T SEE ANY OIL LEAKING ANY PLACE.DON'T KNOW HOW MANY MILES ON THE ENGINE WAS A COUNTY TRUCK ODOMETER READS 120,000 COULD IT BE THAT HAS A BROKEN RING OR MOTOR JUST WORN OUT, OR COULD IT BE AN INJECTOR ?
THE TRUCK HAS GOOD POWER I DON'T UNDERSTAND BECAUSE TO LOOK AT THE TRUCK YOU WOULD THINK IT REALLY DOES HAVE ONLY 120,000 MILES ON IT. IT DOES HAVE A REBUILT TURBO ON IT LESS THAN A YEAR AGO.CAN'T AFFORD THREE TO FOUR GALLONS OF OIL A DAY ANY MORE HOPE YOU CAN HELP SORRY ABOUT THE NOVEL I HAVE JUST WRITTEN BUT WANTED TO TELL AS MUCH AS I COULD THANKS J.C.

Answer
Take the turbo discharge pipe off & look for oil getting into the intake.I would get the blow-by checked but that requires a manometer & adaptor to check.Check air tanks for oil too.An injector want cause oil consumtion.Is it a  STC engine??The STC valve could make it get oil in the fuel.