Can you use sae 0w20 amsoil in place of 5w20?

Yes.

SAE 0W20 means that the oil has zero viscosity in winter. This oil does not exist, which is just as well because if it did it would drain right down into the sump leaving the engine unlubricated.

Several companies make a SAE 0w20, including AMSOIL and Toyota. In cold temperatures the oil is thicker than at warm temperatures. Because it has a lower viscosity, it lubricates the engine faster than a higher viscosity oil. Toyota is specifying 0w20 next year.