Mechanical Energy
Six types of energy:
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Chemical
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Electrical
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Mechanical
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Electromagnetic
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Nuclear
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Thermal
In the combustion reaction chemical energy is changed to thermal energy with is changed to mechanical energy.
What is mechanical energy: Sum of potential and kinetic energies of an object, energy due to motion and position of an object.
Mechanical energy= Kinetic energy + potential energy.
The kinetic energy of the car comes the chemical energy and some of the chemical energy is lost to heat, that is why your car gets hot and you need a coolant in the engine.
But more on specifically the engine:
The piston has potential energy due to pressure on one side, that pressure then moves the piston converting potential to kinetic energy. The piston then moves a crank shaft converting linear kinetic energy to rotational kinetic energy.
It would be nice to note that linear kinetic energy= 1/2mv^2 where:
m is mass in kilograms
v is velocity in meters/second
and kinetic energy comes out in joules
Rotational kinetic energy= 1/2IW^2 where:
I= moment of inertia
W= velocity in radians/second
*I is different for different shapes a lower value of I will give a faster rotational velocity for the same amount of energy
Then the crank shaft hits a low point and because of rotational intertia (L) pushes the piston back up to its original place where the process is repeated. The moving of the crank shaft can then trigger processes to move your car, rotate your lawn blade, or power your boat.
May be useful to know that rotation intertia is the ability of an object to resist changes in rotational motion and it is equal to: L=IW
I= moment of inertia
W=radians/second