[kelnos]

You're probably right that the loss in gas mileage or EV range is pretty small, to the point of being statistical noise.

But a few grams is definitely not correct. It's probably more on the order of 3-5lbs per seat.

If we don't like the heated seat example, let's use power seats. Those are much heavier than the equivalent seat with manual controls to adjust its position and angle. Granted, I don't know of any car manufacturer gating power seats behind a software lock...