Powerstrokes have a hydraulic injection system. The crankcase oil is run through a high pressure oil pump aka "HPOP" and into a piston in the head of the injector. The oil compresses the piston, which compresses the fuel in the lower part of the injector and pushes it out the nozzle. Of course, I'm being very general here and others will probably jump in and give more accurate details.
Big Oil set ups use 2 high pressure oil pumps to feed larger aftermarket injectors. Larger injectors deliver more fuel, but require a larger volume of crankcase oil to maintain the necessary pressures. They don't "use" oil in the same sense a worn out motor uses oil. They just need a bigger supply than factory injectors.