Think of it this way. There is a bar attached to a spindle like they used to use to grind wheat or something. And you are at the end of this bar pushing. Now lets say that nothing is attached to the spindle it is quite easy to push the bar one revolution per minute. Now attach a heavy weight say a 200LB rock to the spindle. Now to maintain that same 1 revolution per minute you have to push much harder or input more energy for the same number of revolutions. In a car the force (equivalent to the mass attached to the bob*g) you are experiencing going up a hill is an increase in the acceleration of the earth i.e. is when you are flat you mainly experience gravity or the earth's acceleration of the mass of your car directed through the center of mass of the car straight towards the ground which does not affect your forward motion. When the car is at an angle to the direction of the earth's gravitational field (acceleration) then it does affect your forward motion in addition to the previous resisistors to motion (friction). Torque is measured in energy and to maintain the same number of rotations you have to have more torque or more energy which in this case is extracted from petrol.

Torque which is defined as radius (or distance from the application of force to the center of mass of the object being acted upon) X (cross product not multiplication) Force you are exerting. In the above case r = the distance from your hands on the bar to the spindle, Force = the acceleration you have to apply to the bar * the mass applied to the spindle.

Torque is measure in units of energy (kg m^2 s^-2 = Joule)
The equations are here:

http://scienceworld.wolfram.com/physics/Torque.html