Thermodynamics

536 | ThermodynamicsFIGURE 9–65Air conditioning increases fuelconsumption by 3 to 4 percent duringhighway driving, and by as much as10 percent during city driving.FIGURE 9–66Proper maintenance maximizes fuelefficiency and extends engine life.Use the Air Conditioner SparinglyAir-conditioning consumes considerable power and thus increases fuel consumptionby 3 to 4 percent during highway driving, and by as much as 10 percentduring city driving (Fig. 9–65). The best alternative to air-conditioning isto supply fresh outdoor air to the car through the vents by turning on the flowthroughventilation system (usually by running the air conditioner in the“economy” mode) while keeping the windows and the sunroof closed. Thismeasure is adequate to achieve comfort in pleasant weather, and it saves themost fuel since the compressor of the air conditioner is off. In warmer weather,however, ventilation cannot provide adequate cooling effect. In that case wecan attempt to achieve comfort by rolling down the windows or opening thesunroof. This is certainly a viable alternative for city driving, but not so onhighways since the aerodynamic drag caused by wide-open windows or sunroofat highway speeds consumes more fuel than does the air conditioner.Therefore, at highway speeds, the windows or the sunroof should be closedand the air conditioner should be turned on instead to save fuel. This is especiallythe case for the newer, aerodynamically designed cars.Most air conditioners have a “maximum” or “recirculation” setting thatreduces the amount of hot outside air that must be cooled, and thus the fuelconsumption for air-conditioning. A passive measure to reduce the need forair conditioning is to park the vehicle in the shade, and to leave the windowsslightly open to allow for air circulation.AFTER DRIVINGYou cannot be an efficient person and accomplish much unless you take goodcare of yourself (eating right, maintaining physical fitness, having checkups,etc.), and the cars are no exception. Regular maintenance improves performance,increases gas mileage, reduces pollution, lowers repair costs, andextends engine life. A little time and money saved now may cost a lot later inincreased fuel, repair, and replacement costs.Proper maintenance such as checking the levels of fluids (engine oil, coolant,transmission, brake, power steering, windshield washer, etc.), the tightness ofall belts, and formation of cracks or frays on hoses, belts, and wires, keepingtires properly inflated, lubricating the moving components, and replacingclogged air, fuel, or oil filters maximizes fuel efficiency (Fig. 9–66). Cloggedair filters increase fuel consumption (by up to 10 percent) and pollution byrestricting airflow to the engine, and thus they should be replaced. The carshould be tuned up regularly unless it has electronic controls and a fuelinjectionsystem. High temperatures (which may be due to a malfunction ofthe cooling fan) should be avoided as they may cause the break down of theengine oil and thus excessive wear of the engine, and low temperatures(which may be due to a malfunction of the thermostat) may extend theengine’s warm-up period and may prevent the engine from reaching the optimumoperating conditions. Both effects reduce fuel economy.Clean oil extends engine life by reducing engine wear caused by friction,removes acids, sludge, and other harmful substances from the engine, improvesperformance, reduces fuel consumption, and decreases air pollution. Oil alsohelps to cool the engine, provides a seal between the cylinder walls and the