Wind resistance increases by the square of the speed of the vehicle — it’s 4 times worse at 60 mph than at 30 mph.
Stop and go city driving uses up energy to accelerate the vehicle’s mass. Hybrid vehicles recover part of that energy when braking — therefore, they can get better mileage in the city than on the highway.
Speaking of wind resistance and aerodynamic drag : some 90% of your gas-energy becomes waste heat thru the tail pipe/radiator, only some 10% goes to compressing air on the front and rarifying it on the back. Essentially the vehicle is a FISH or BIRD moving thru a fluid. And yet here you see the collective stupidity of car/truck designers : square backs = low pressure from explosive decompression on the BACK(= SUCTION), vs tapered fish/bird tails that allows gentle, laminar recollapse of the rearward-going air/fluid.
A box has 14 times the wave drag as a torpedo shape, thus over the years you’ve seen more and more aeroshells on semitruck cabs as the fish head; but where is the TAPERED TAIL? Thus the rear suction = dust/dirt on the flat rear doors = energy loss due to wave drag.
Google NASA, the tapered tail on the shuttle for its piggyback ride on a 747; and DYMAXION CAR. You see, in the 1930s they designed streamlined cars with TAPERED TAILS; then collective stupidity set in. About the only intelligent design still on the road is the VW bug.
So, look in the mirror for vehicle energy efficiency : who’s the smarter one, the “genius” looking back at you, or “dumb” fish/birds that have been around a lot longer than car/truck designers...