Mobil HyJet IV-Aplus is a fire-resistant phosphate ester hydraulic fluid for use in commercial aircraft. It is the best-performing Type IV fluid and approaches many of the performance capabilities of Type V fluids, including high temperature stability, long fluid life, low density, and rust protection. It is superior to all other Type IV fluids in these respects. Mobil HyJet IV-A plus meets the specifications of all major aircraft manufacturers and SAE AS1241.