since i live in a hilly area, when car is going down hill i shift to neutral and let the car run thru principle of enertia. when it reach the flat rd and speed is down then i shift it back to dr. you ca turn off the engine in some car but on newer car , it will affect the brake and power steering..also turn off engine on stop light if in your calculation will take more than 2 to 3 minutes wait. drive within 65 mph .check tire pressure, air filter and change oil every 3 to 5k miles.the other optional thing is to plan ahead your erand duty on your way home,cutback on unnesesary travel,use your phone.pay your bill online saving on stamp and driving to post office .