The ROBINSON A257-4 is a specified Type “A” Automatic Transmission Fluid (ATF) used in various Robinson helicopter systems, primarily as a hydraulic/lubrication fluid in rotor system components and related mechanical assemblies (depending on model and subsystem).

It is typically equivalent to Dexron III / Mercon ATF and is used where controlled viscosity, anti-wear additives, and stable hydraulic performance are required under varying temperature and load conditions in helicopter operations.

Within Robinson maintenance documentation (R22 / R44 / R66 series), A257-4 is listed as an approved standard lubricant for specific gearbox and mechanical lubrication points, particularly in rotor head and spindle-related assemblies (depending on model and revision).

Key features include:

OEM Robinson-approved lubricant specification (A257 series)
Type “A” ATF formulation (Dexron III / Mercon equivalent)
Used in helicopter rotor and mechanical lubrication systems
Stable viscosity across wide temperature range
Anti-wear and anti-foaming additive package for rotor system use
Compatible with sealed helicopter gear and spindle assemblies
Designed for vibration-heavy rotary-wing environments
Replaced or supplemented by updated A257-25 in some applications
Used in Robinson R22 / R44 / R66 maintenance procedures
Must not be mixed with incompatible lubricant types
Supports hydraulic-like load conditions in rotor system components