> - Driving on the highway rather than around town (see the 50 MPH comment)
That would greatly depend on the town one is picturing. In pretty much any neighborhood in LA, there's no way you're going to sustain a speed of 50 mph for any reasonable period of time without frequently stopping at intersections, your usual traffic congestion, pedestrians wandering into the street, other drivers making idiotic maneuvers, etc. No way is your mileage going to be better on surface streets even if you do your best to reach 50 mph but not exceed it. Frequently braking and accelerating requires more gas than will be eaten up by driving at a constant speed of 65 mph.
That would greatly depend on the town one is picturing. In pretty much any neighborhood in LA, there's no way you're going to sustain a speed of 50 mph for any reasonable period of time without frequently stopping at intersections, your usual traffic congestion, pedestrians wandering into the street, other drivers making idiotic maneuvers, etc. No way is your mileage going to be better on surface streets even if you do your best to reach 50 mph but not exceed it. Frequently braking and accelerating requires more gas than will be eaten up by driving at a constant speed of 65 mph.