Because of the nature of how this system operates, air in the fuel is not as great of a concern as air in the oil. The PowerStroke requires a special anti-foaming agent in its oil to prevent this aeration. Oils with an API service rating of CF-4 or CG-4 already have this agent, but it becomes depleated as the oil breaks down, so regular oil changes (3000-5000 miles depending on vehicle use) are necessary. The anti-foaming agent can also be depleated by interaction with some silicone sealers.

What has been done on the PowerStroke is both of these systems are used in conjuntion with each other. Fuel is supplied to the injectors through fuel rails inside the cylinder heads. Also supplied to the injectors is high pressure engine oil. As the computer determines that a cylinder should fire it signals the Injector Driver Module. The IDM sends a 110 volt pulse-width modulated signal to the injector solenoid. When the injector solenoid is actuated, it opens a poppet valve which allows high pressure oil to flow into the intensifier piston. The intensifier piston is forced down, pressurizing the fuel inside the injector. When fuel pressure inside the injector reaches approximatly 2700 psi, it causes the injector pintle to rise off its seat and fuel is injected into the cylinder from the nozzel. As long as the poppet valve is open and oil is flowing into the injector, fuel will be injected.

The computer controls how long the injector solenoid is energized (pulse-width, or time on in milliseconds), but it also determines the pressure of the fuel being injected by controlling the pressure of the oil (IPR duty-cycle, or the percentage of time on vs. off--AKA dwell) in the cylinder heads. The computer determines this based on engine load and driver demand by monitoring various sensors. Since the cavity at the top of the intensifier piston is seven times the size of the fuel cavity at the bottom, fuel is injected at a pressure seven times that of the computer-controlled oil pressure--oil pressure 3000 psi = injected fuel pressure 21000 psi. Due to the high oil system pressures, the spring which closes the poppet valve once the injector solenoid is deactivated has to be very strong--and because of this, the solenoid needs to be 110 volts. Once the poppet valve is closed, spring pressure returns the injector to its normal state and the oil is exhausted into the valve cover area to return to the sump.

Because of the nature of how this system operates, air in the fuel is not as great of a concern as air in the oil. The PowerStroke requires a special anti-foaming agent in its oil to prevent this aeration. Oils with an API service rating of CF-4 or CG-4 already have this agent, but it becomes depleated as the oil breaks down, so regular oil changes (3000-5000 miles depending on vehicle use) are necessary. The anti-foaming agent can also be depleated by interaction with some silicone sealers.

Recommended anti-foaming additives are Fleetrite with the Navistar P/N CH1824392 or Lubrizol 888. These are primarilly used to counter the effects of silicone sealers on the anti-foaming agents in the oil or if the agents become depleted from use providing the oil is still servicable and uncontaminated. An anti-foaming additive could also be used between oil changes if an oil-related poor running condition is suspected, especially on a long trip.
Under normal driving conditions the additive could extend the oil change interval to 6000 miles. For vehicles that are used for infrequent towing, using the additive at 3000 miles could extend the oil change interval to no longer than 5000 miles. Vehicles operated in dirty conditions, extreme weather conditions or constantly under heavy loads should stick to the 3000 mile service interval due to the other agents in the oil being depleted, and should only use the anti-foaming additive if performance problems occur between services.