I just purchased this but I have no clue on how to start using the Propane. Any help is greatly appreciated. I'm at Toronto West.

On the left hand side there's a button I was told that by pressing it it would switch to propane? Am i supposed to press for a long time?

The switch button has 3 lights 2 of which are highlighted in green and just below theres a G with a green light.

Also, if you can help me determine how fuel consumption on a truck works. Here is the scenerio Distance from A to B according to google map is 10.2km.
On the fuel tank indicator it said that I have 79km left of fuel>>> by the time I got to place "B" there was 38km of fuel left? Is this correct?