Real-world data: Heading west from Amarillo on I-40 at 65 mph into a 20 mph headwind (per Tesla Waze), I was using 410 kWh/mi and running well below the trip power curve. After tucking in 2-3 secs behind a truck (a cab towing a pair of cabs), consumption dropped to around 350 kWh/mi and I gradually recovered to the curve (well, close enough for comfort).
Traffic wasn't too heavy, visibility was excellent, and I never had the feeling that I couldn't react to traffic. I'm driving a classic P85, so autopilot didn't come into play.
Woof. 350 kWh/mi is a definite improvement, but you'd still only go about 1/4 mile. Methinks you mean Wh/mi.