Traffic Signal Alert. One more trick to save your petrol and diesel while driving is to follow the traffic signal alert rule. When you are nearing a traffic signal, slow down your vehicle slowly and turn it off. We wait for a lot of time while we are at the traffic signal and if you keep your vehicle on for that time, it means all that fuel is being wasted. Waiting for the traffic light to turn green takes at least one minute and if you close the engine, then your fuel will be saved. The petrol used in restarting the motor vehicle will be comparatively less than the one lost during the time you were waiting at the signal. Also, when the light turn greens, avoid accelerating too fast. This will also save your petrol and diesel to a great extent.