A method of purging air from an oil passage in communication with a lifter assembly in an engine assembly may include isolating the oil passage from a pressurized oil source while the lifter assembly is engaged with a base region of a cam lobe to operate the first lifter assembly in the activated mode. The pressurized oil may be provided to the lifter assembly via the oil passage after the isolating when the lifter assembly is engaged with a lift region of the cam lobe. The lifter assembly may be maintained in the activated mode after the providing. Air may be purged from the oil passage based on the pressurized oil provided to the oil passage.