What is the MIL-SPEC number for the engine oil in the F/A-18 E/F?

The MIL-SPEC number for the engine oil used in the F/A-18 E/F is indeed MIL-PRF-23699. This specification defines the standards for the type of jet engine oil required for aircraft such as the F/A-18 E/F, ensuring that the oil can perform effectively under the extreme conditions encountered in military aviation. MIL-PRF-23699 is specifically designed to provide adequate lubrication and protection for high-performance engines operating at wide temperature ranges, which is crucial for maintaining operational readiness and performance.

In contrast to the other options, MIL-PRF-23687 is another type of jet engine oil but has different properties and is not specified for use in the F/A-18 E/F. MIL-PRF-83281 is a specification for hydraulic fluids used in aircraft systems, and MIL-PRF-5606 is a specification for mineral-based hydraulic fluids, neither of which apply to engine oil. Thus, recognizing the correct MIL-SPEC number is essential for proper maintenance and operation of the aircraft engine.