Actually from Tahoe to Sac is probably one of the better stretches to pull that off, it’s all downhill.

That doesn’t change the gist of your comment however - which is correct. (I’m a happy Bay Area Rivian owner who’s made that trip often)

Tahoe to Sac for sure isn't bad. The uphill section before that adds 2-3 gallons by itself when I'm towing though (compared to a flat route the same distance and speeds). IIRC net fuel economy winds up being similar to a flat stretch (even the downhill stretch burns a lot of energy in your brakes and has enough flat and uphill segments -- slightly ameliorated with regenerative braking, but I don't think it moves the needle enough).

How is your Rivian by the way? Is it in any way comparable to a cybertruck or is it just far and away better?