In automobiles, a start-stop system or stop-start system automatically shuts down and restarts the internal combustion engine to reduce the amount of time the engine spends idling, thereby reducing fuel consumption and emissions.
For non-electric vehicles fuel economy gains from this technology are typically in the range of 3-10 percent, potentially as high as 12 percent.
On a manual transmission vehicle, stop-start is activated as follows: Stop car and press clutch - move gear lever to neutral - release clutch - then the engine stops.
The engine won't stop if the car is moving, even if the aforementioned steps are followed (note that this isn't true for all cars).