..it's also worth remembering that a large portion of the Engines power is taken up driving the Dynamo/Generator supplying the lights during darkness, so I always turn off my headlights when stopped in a traffic queue...
...there is no point in wasting Petrol/Diesel blinding/annoying the driver in front, via his rear-view mirror, when the traffic is stationary!
Add-up the Watts consumed by all your lights, and convert that into HP (Horse Power) required by the engine...

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As a Motorcyclist I ride with my headlights on for safety reasons, during daylight, but as above, I always witch them off when stationary...

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Paul.... 8-)...!
Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.