It would seem so. I switched the 01 Impala from one Amsoil ATF to another:
Amsoil O.E. Fuel Efficient ATF:
Kinematic Viscosity @ 100˚C, cSt (ASTM D445) -- 5.8
Kinematic Viscosity @ 40˚C, cSt (ASTM D445) --- 28.3
Amsoil Signature Series Fuel Efficient ATF:
Kinematic Viscosity @ 100˚C, cSt (ASTM D445) -- 6.3
Kinematic Viscosity @ 40˚C, cSt (ASTM D445) --- 30.8
The car was getting 1 MPG better, roughly speaking, on the O.E. ATF. I'm probably not changing it again until 2023, at least.
Data Sheets (Sources: )
O.E.:
https://www.amsoil.com/lit/databulletins/g3190.pdf
Sig. Series:
https://www.amsoil.com/lit/databulletins/g3110.pdf