question: Why should I let my car run in cold weather?
comment: If you turn on the engine, and immediately begin to do something that requires significant energy, the engine will begin working faster. This in turn, as we use combustion engines, generates heat, assuming your car has been out in the cold, your rather massive engine block stores said cold very well. So, by rapidly pushing out extreme heat into metal that is already very cold, the outermost parts of the metal expand while the inner parts stay cool. This causes strain that will overall shorten the life of the engine, but not cause significant harm on its own. The effect can be seen on a more visible scale when you pour hot water onto cold glass
passages: Cold starts are more difficult than starting a vehicle that has been run recently (typically between 90 minutes and 2 hours). More effort is needed to turn over a cold engine for multiple reasons:
  
  BULLET::::- The engine compression is higher as the lack of heat makes ignition more difficult
  
  BULLET::::- Low temperatures cause engine oil to become more viscous, making it more difficult to circulate.
  
  BULLET::::- Air becomes more dense the cooler it is. This affects the air-fuel ratio, which in turn affects the flammability of the mixture.
  
  Section::::Solutions to cold starting.
   Research by the Agricultural Engineering Department of the University of Saskatchewan has shown that operating a block heater for longer than four hours prior to starting a vehicle is a waste of energy. It was found that coolant temperature increased by almost degrees in that period, regardless of the initial temperature. Four tests were run at ambient temperatures ranging from ; continued use of the heater for a further one or two, or more, hours achieved a mere 2 or 3 more degrees Celsius as conditions stabilized. Engine oil temperature was found to increase over these periods by just .
   While gasoline internal combustion engines are much easier to start in cold weather than diesel engines, they can still have cold weather starting problems under extreme conditions. For years, the solution was to park the car in heated areas. In some parts of the world, the oil was actually drained and heated over night and returned to the engine for cold starts. In the early 1950s, the gasoline Gasifier unit was developed, where, on cold weather starts, raw gasoline was diverted to the unit where part of the fuel was burned causing the other part to become a hot vapor sent directly to the intake valve manifold. This unit was quite popular until electric engine block heaters became standard on gasoline engines sold in cold climates.
   Equipment designed for use in particularly extreme cold conditions (such as the polar regions) also undergoes a "winterization" process. Many complex devices (automobiles, electronics and radios) as well as common materials (metals, rubbers, petroleum lubricants) are not designed to operate at extremely low temperatures and must be winterized to operate without severe damage from the elements in such conditions. This might involve a chemical treatment process, additional waterproofing/insulation, or even the total substitution of new parts. An example would be the internal combustion engine of an automobile; the installation of heaters on the engine block and battery as well as the substitution of winter-grade coolants and lubricants allows the vehicle to start and run in sub-freezing conditions where a non-winterized engine would quickly break down.
   Cold start (automotive)
  
  A cold start is an attempt to start a vehicle's engine when it is cold, relative to its normal operating temperature, often due to normal cold weather. A cold start situation is commonplace, as weather conditions in most climates will naturally be at a lower temperature than the typical operating temperature of an engine. Occasionally, the term also refers to starting the engine of a vehicle that has been inactive or abandoned for a significant amount of time such as months, years or even decades.
  
  Section::::Causes of cold starts.
   Cars and trucks using direct air cooling (without an intermediate liquid) were built over a long period from the very beginning and ending with a small and generally unrecognized technical change. Before World War II, water-cooled cars and trucks routinely overheated while climbing mountain roads, creating geysers of boiling cooling water. This was considered normal, and at the time, most noted mountain roads had auto repair shops to minister to overheating engines.
   As the fuel filter is the first point to become clogged up, most diesel motor cars are equipped with a filter heater. This allows summer diesel with a CFPP of –7 °C to be operated safely in –20 °C weather conditions. The fluid characteristics of winter diesel are also extended allowing a diesel type of CFPP –15 °C to be operated safely in –24 °C weather conditions. Note that a filter heater cannot melt wax particles in the "feed system" so that fuel supply can be problematic at cold start.
  
  Section::::Operation.:Additives.
   Section::::Practice.
  
  Practice days are on Sunday and Monday from 8:00 AM till 5:00 PM. In the middle of the day, practice sessions are sorted into 1/8 and sedan classes. No fuel bottles or refueling is allowed inside the fenced-in track area to allow all drivers the chance to get practice. Severe penalties from the officials for breaking this rule include reprimands, loss of fuel bottle or being sent home.
  
  Section::::Qualifying.
   power could be put down, therefore making the car faster in such conditions.
   Since the heater core relies on the coolant's heat to warm the cabin air up, it obviously won't begin working until the engine's coolant warms up enough. This problem can be resolved by equipping the vehicle with an auxiliary heating system, which can either use electricity or burn the vehicle's fuel in order to rapidly bring the engine's coolant to operating temperatures.
  
  Section::::Air cooled engines.
   BULLET::::4. In the air conditioning test, the ambient temperature of the test cell is raised to 35 °C. The vehicle's climate control system is then used to lower the internal cabin temperature. Starting with a warm engine, the test averages 35 km/h and reaches a maximum speed of 88 km/h. Five stops are included, with idling occurring 19% of the time.
   BULLET::::- The several feet of plumbing going back and forth between the engine compartment and trunk proved unreliable in service.
  
  BULLET::::- The price, at US $274 ($4,692.12 in 2014 US dollars), was unaffordable to most people in depression/pre-war America.
  
  The option was discontinued after 1941.
  
  Section::::History.:Chrysler Airtemp.
   The trustworthiness of the EN 590 have been criticized as being too low for modern diesel motors – the German ADAC has run a test series on customary winter diesel in a cold chamber. All diesel brands did exceed the legal minimum by 3 to 11 degrees in the laboratory according to the legal DIN test. One of the real diesel motors however stopped working even before the legal minimum was reached, presumably due to an undersized filter heater. Notably the experiments did not show a direct correlation between the CFPP value of the mineral oil and the cold start capability of the diesel motors – hence the automobile club suggest the creation of a new test standard.
   The engine produces high temperatures under full application and thus causes a high temperature variation in the engine bay from no operation to normal and full operation. CFRP becomes mechanically stressed over time from high heat transfer effects and thus the engine bay was not constructed from CFRP.
  
  Section::::Design and implementation.:Aerodynamics.
   Some cars, such as the second generation Toyota Prius, pump hot coolant from the cooling system into a 3-litre insulated thermos-style reservoir at shutdown, where it stays warm for up to 3 days.
  
  Section::::History.
   The method provides no hard and fast rules about what lines of questions to explore, or how long to continue the search for additional root causes. Thus, even when the method is closely followed, the outcome still depends upon the knowledge and persistence of the people involved.
  
  Section::::Example.
  
  BULLET::::- The vehicle will not start. (the problem)
  
  BULLET::::1. Why? - The battery is dead. (First why)
  
  BULLET::::2. Why? - The alternator is not functioning. (Second why)
  
  BULLET::::3. "Why?" - The alternator belt has broken. (Third why)
   The problem of cold starting has been greatly reduced since the introduction of engine starters, which are now commonplace on all modern vehicles. The higher revs that can be achieved using electric starter motors improves the chance of successful ignition.
  
  Starting fluid, a volatile liquid, is sometimes sprayed into the combustion chamber of an engine to assist the starting procedure.
   Lithium-ion batteries operate best at certain temperatures. The Model S motor, controller and battery temperatures are controlled by a liquid cooling/heating circuit. Waste heat from the motor heats the battery in cold conditions, and battery performance is reduced until a suitable battery temperature is reached.
   Finally, other concerns may dominate cooling system design. As example, air is a relatively poor coolant, but air cooling systems are simple, and failure rates typically rise as the square of the number of failure points. Also, cooling capacity is reduced only slightly by small air coolant leaks. Where reliability is of utmost importance, as in aircraft, it may be a good trade-off to give up efficiency, longevity (interval between engine rebuilds), and quietness in order to achieve slightly higher reliability; the consequences of a broken airplane engine are so severe, even a slight increase in reliability is worth giving up other good properties to achieve it.
   MYs 1984 and 1985 came with a double row timing chain from the factory to address this issue.
  
  Another problem area for late 450 SLs was the automatic climate control system. Based on a "servo", which controlled coolant flow to the heater core, as well as vacuum to actuate the vents in the interior of the car, the system proved unreliable. It was installed on 450 SLs through end of production in 1980. Models produced prior to 1976 had a manual climate control system, 380SL models produced from 1981 received a more reliable automatic climate control system.
   The temperature of the cooling air may range from well below freezing to 50 °C. Further, while engines in long-haul boat or rail service may operate at a steady load, road vehicles often see widely varying and quickly varying load. Thus, the cooling system is designed to vary cooling so the engine is neither too hot nor too cold. Cooling system regulation includes adjustable baffles in the air flow (sometimes called 'shutters' and commonly run by a pneumatic 'shutterstat); a fan which operates either independently of the engine, such as an electric fan, or which has an adjustable clutch; a thermostatic valve or just 'thermostat' that can block the coolant flow when too cool. In addition, the motor, coolant, and heat exchanger have some heat capacity which smooths out temperature increase in short sprints. Some engine controls shut down an engine or limit it to half throttle if it overheats. Modern electronic engine controls adjust cooling based on throttle to anticipate a temperature rise, and limit engine power output to compensate for finite cooling.
   The Czech Republic–based company Tatra is known for their large displacement air-cooled V8 car engines; Tatra engineer Julius Mackerle published a book on it. Air-cooled engines are better adapted to extremely cold and hot environmental weather temperatures: you can see air-cooled engines starting and running in freezing conditions that seized water-cooled engines and continue working when water-cooled ones start producing steam jets. Air-cooled engines have may be an advantage from a thermodynamic point of view due to higher operating temperature. The worst problem met in air-cooled aircraft engines was the so-called "Shock cooling", when the airplane entered in a dive after climbing or level flight with throttle open, with the engine under no load while the airplane dives generating less heat, and the flow of air that cools the engine is increased, a catastrophic engine failure may result as different parts of engine have different temperatures, and thus different thermal expansions. In such conditions, the engine may seize, and any sudden change or imbalance in the relation between heat produced by the engine and heat dissipated by cooling may result in an increased wear of engine, as a consequence also of thermal expansion differences between parts of engine, liquid-cooled engines having more stable and uniform working temperatures.
   BULLET::::4. Why? - The alternator belt was well beyond its useful service life and not replaced. (Fourth why)
  
  BULLET::::5. Why? - The vehicle was not maintained according to the recommended service schedule. (Fifth why, a root cause)
   The United States Office of Defense Transportation implemented mandatory pooling of class RS produce refrigerator cars from 1941 through 1948. World War II experience found the cars spending 60 percent of their time traveling loaded, 30 percent traveling empty, and 10 percent idle; and indicated the average 14 loads each car carried per year included 5 requiring bunker icing, 1 requiring heating, and 8 using ventilation or top icing.
  
  Following experience with assorted car specifications, the United Fresh Fruit and Vegetable Association (UFF&VA) listed what they considered the best features of ice refrigerator cars in 1948:
   Very young children can perish from heat or cold if left unattended in a parked car, whether deliberately or through absent-mindedness. In 2004, the U.S. NHTSA estimated 25 fatalities per year among children left in hot cars.
  
  Section::::Issues for particular demographic groups.:Teenage drivers.
  