[JimmyEV]

Rivian has confirmed by an email that their quad-motor system is full time all-wheel drive. I might've thought there'd be a front-wheel drive or rear-wheel drive setting as an economy mode to improve range but that's not the case.

 

[timesinks]

I'm not an expert here, but I think the inefficiencies in ICE AWD systems come from the mechanical linkages via differentials. Considering each wheel is independently driven, you don't have those losses on the Rivian. For equal power output, splitting that over 4 motors instead of 2 means less current to each motor and therefore less electrical loss from resistance in the system. So I suspect full-time awd is the most efficient operational state -- but I'm just a layman when it comes to electrical and mechanical engineering.