The most fuel efficient way to drive is to drive at a constant speed on the highway.
It's best to drive at around 65 MPH to 55 MPH depending on the speed limit on the road and even though some Interstates allow 70 MPH it's better to stay at around 65 MPH as the more you press the gas pedal the more gasoline will be used.
It is more fuel efficient to drive on the highway vs in town driving.
When you're driving on the highway at a constant speed you're covering more miles and using less fuel to cover those miles.
Driving in town uses more fuel as you constantly start and stop and the engine is still using fuel but not moving as fast or as far.
Cars and vehicles are much more fuel efficient when driving at highway speeds and it's also easier on the cars transmission and engine to drive on the highway instead of in town.
The stopping and going can wear your transmission out faster and wear your engine out faster than doing mostly highway driving.
Highway driven miles are better on a vehicle than just in town driving and the engine produces less sludge when driving on the highway as the engine gets to and stays at operating temperature.
Using more energy means using more gasoline to generate it, which is why vehicles get fewer miles per gallon in urban driving than they do on interstates and highways.
There is an exception to this rule, however. Unlike traditional gas engine automobiles, hybrids get better gas mileage in the city than the highway.