History and Advances in the Four stroke Engine The four stroke engine has come a long way since its first introduction to society. Now instead of carburetors, points and condenser style ignition systems, which were very inefficient at using all of the fuel, entering the system; today’s engines use computers to analyze and monitor the emissions and performance of the engine. These computers give the engine the precise ratio of fuel to air so that the engine may have as complete combustion as is possible, the computer takes in factors such as fuel grade (premium fuel or regular), outside temperature, engine temperature, barometric pressure, altitude, and air quality and matches the fuel curve for all theses factors. The advancement of computers in automobiles has helped fuel efficiency increase by over a 50 percent since 1969. There are still several major flaws in the internal combustion engine process that can be improved upon.  These are energy losses of the combustion cycle. Of the one hundred percent of the power in the combustion in an engine, 36% goes to water heating, 38% to exhaust heat, 6% to motor friction (friction loss of the motor can reach double or even triple this amount if the engine is not in good working order or the temperature is below freezing). So, of the initial 100% of power, we now have 20% which is reduced down even lower when we look at other forces acting on the vehicle; such as 2% that is taken away by the drive train and another 3% taken by the tires and 8% taken by the air resistance acting on the car. This leaves 7% of the initial 100% to accelerate and use to run accessories. Today’s vehicles are vastly more efficient than the vehicle of the past, but with prices rising for fuels and a realization that these fuels may someday run out we must keep looking for ways to improve vehicle efficiency. Some of the ways this can and is being done, is to use more aerodynamic cars and use engines with smaller tolerances to cut down on friction. Yet, mainly since the 4 stroke combustion process has been refined nearly to its most efficient level with the fuels we use today (gasoline and diesel); we now we must look not only at alternative fuel sources but also at different types of engines (such at rotary power), so that we can keep transportation as economical as possible; not to mention the preservation of resources and less pollution of the environment.