Automotive Urban Legends Revealed!


? Hybrid vehicles save fuel by running on electricity instead of gasoline or diesel fuel etc.   MOSTLY FALSE!!      Excluding vehicles adapted to draw from an external power source: 100% FALSE!!  Excluding for now vehicles that can have their batteries recharged from the power company, the hybrid vehicle DERIVES 100% OF ITS PROPULSION AND POWER FOR LIGHTING, STEREO, AC ETC. FROM ITS FUEL TANK.  When the gasoline (or diesel) engine is off the vehicle is running on surplus power from that gasoline or diesel engine which was converted into electricity and stored in the batteries.  When the vehicle is going downhill and using not traditional friction braking but rather "regenerative" braking the batteries are recharged.  This is not free, however.  Ultimately 100% of the energy being stored in the batteries came from the traditional engine and the fuel tank.  It might be the last time the vehicle accelerated or climbed the hill or considerably earlier but it all came originally from the fuel tank.  So how does hybrid technology enhance fuel mileage?  Every time energy is converted from one form to another, for example from the kinetic energy of a 50 mph speed to electricity, from fuel burned in an internal combustion engine to electricity stored in batteries, from battery charge to vehicle movement through electric motors, some is wasted because no man-made mechanism is 100% efficient.  However, turning some of the energy that got the vehicle up to speed into electricity to recharge batteries -- using generators for braking -- reclaims for future use a percentage of that energy derived from burning a fuel.  Traditional friction braking reclaims none -- its all turned into heat to be dissipated to the atmosphere by the brake drums and rotors.  (If the car received a brake job at a typical brake franchise a significant amount of the energy might be converted into sound).  Very sophisticated computer programming ensures that the traditional internal combustion engine will run only at the highest possible mode of efficiency through the elimination of idling and other wasteful modes.  The battery and electric motor portion of the drivetrain is essential to provide a means to store and use later the extra power produced when the traditional engine is running.  The vehicle might be able to stop and go several times from what is stored in the batteries before there is a need to start the traditional engine but when that happens be assured it will run with the maximum efficiency state-of-the-art engineering allows.  

What about vehicles plugged in at night?  Depending on driving scenarios such a vehicle might be operated indefinitely never taking a drop from the fuel tank.  Unfortunately, it will be ultimately powered primarily by coal in most areas or perhaps by nuclear means.  The electric company that generates significant power from wind, or solar panels is rare indeed.  In some areas hydroelectric power is significant.  By and large, however, the electricity, and hence the propulsion of the vehicle plugged in the night before, comes from burning a fossil fuel.  There's still pollution but it has been relocated.  The relative amounts of pollution from a modern gasoline engine versus coal burned in a modern power plant and the relative gasoline versus electric bill costs are WAY beyond the scope of this piece -- and also my knowledge!                   

 

? It's somehow harmful to start your car without first turning off the radio, air conditioner etc. FALSE!!  The current these devices draw is negligible compared with what the starter requires.  In any case the ignition switch disables them in the start position.  Even leaving the lights on during cranking will have little effect given anything better than the most marginal battery.

    

?  Storing car batteries directly on a cement floor drains their energy.  FALSE!!  Putting a piece of wood under the battery -- advisable according to legend -- serves no purpose.  The plastic case is far more than adequate to block electrical leakage from inside the battery.  It is true that batteries gradually self-discharge internally.  Also, the colder they are the less of whatever electrical energy they contain is immediately available.

 

?  Coca-Cola is good for cleaning battery connections.  FALSE!!  This flies in the face of basic chemistry.  The whole problem with battery connections is corrosion due to their acidic environment.  Carbonated beverages are acidic and cannot neutralize the troublesome battery acid.  Baking soda is alkaline and hence a far better choice.

 

?  Greedy gas station proprietors sometimes water down the fuel they sell.  FALSE!!  We all know that water and oil don't mix.  Like oil, gasoline is a petroleum product that won't mix with water.  Water in the underground tanks will sink and whoever is unlucky enough to pump it into his or her tank will probably not make it more than a hundred yards.  It is possible to emulsify a small amount of water with gasoline through the addition of a co-solvent of the alcohol family such as methanol.

 

?  Overfilling an engine or transmission will blow out seals. FALSE!!  The inside of an engine produces the potential of pressure primarily due to heat.  Also, a little bit of combustion exhaust inevitably leaks past the piston rings and is called "blowby."  For this reason the crankcase is vented to outside atmospheric pressure or even has slight vacuum applied to prevent forcing oil out of every seal and gasket.  All transmissions and differentials are vented to accommodate heat build-up and barometric pressure changes.  Overfilling an engine, transmission or differential may well overflow oil out the vent or elsewhere but will NOT damage seals.

 

?  Don't let your gas tank get nearly empty or accumulated crud from the bottom of tank will get sucked up causing fuel system problems.  MOSTLY FALSE!!  The pickup screen for the fuel pump is at the bottom of the tank and ALWAYS pulls from there.  Particularly in cold climates, however, it is wise to keep the tank relatively full so there is less exposed surface area inside the tank where condensation could occur to contaminate the fuel with rust particles and water.  Running out of gas is stressful to the in-tank electric fuel pump in modern vehicles as which relies on fuel for cooling and lubrication.

 

?  There have been devices invented that allow an ordinary car to get 100 or more miles per gallon with drastically reduced emissions, increased power and no engine wear.  They have been suppressed by the oil companies or car manufacturers.  FALSE!!  No need to say much about this one, but I will point out that if fuel line magnets and such had even a slight benefit you can bet they would be used in the racing community which will do anything for even the slightest edge.  Needless-to-say, racers don't waste their time with such.  There have been variations on this myth for as long as there have been automobiles. 

 

?  The higher the octane of the fuel you put in your tank, the more horsepower, the more miles per gallon.  TRUE UNDER SPECIFIC CIRCUMSTANCES!!  This has been widely believed for many decades and, until relatively recently was false.  Octane is NOT a rating of the amount of energy in a gallon of gasoline, nor it's detergent qualities.  Octane refers specifically to the gasoline's resistance to entering an undesirable truly explosive mode of combustion causing "knock" or "ping" -- encouraged by heavy engine load, high temperatures, high compression, advanced timing and other factors.  On a pre-computer vehicle higher octane than necessary to prevent excess pinging was strictly money down the toilet.  Timing, high compression ratios and high engine temperatures are key to a different situation now.  In a modern computer-controlled vehicle these parameters are pushed close to, and sometimes beyond the limit where pinging occurs.  This is done in the interest of reduced emissions, greater fuel efficiency and performance.  When tolerances are such that the limit is exceeded a device called a "knock sensor"  -- essentially a tuned microphone -- picks up the sound of the "ping" and signals the on-board computer to retard ignition timing until most of the harmful "pinging" is suppressed  --  to the detriment of horsepower and fuel mileage.  High octane fuel reduces this compromise.

                          

?  An environmentally responsible citizen never uses the air conditioner of his or her older car that contains R12 freon -- a substance known to damage the ionosphere.  FALSE!!  The system is under pressure even when the car is turned off -- the suction side higher in pressure than with the AC in use and the discharge side lower -- but prone to leakage in any case.  In some ways more so if allowed to atrophy because refrigerant oil is not circulated to discourage corrosion of fittings and deterioration of "o"- rings and seals.  The use of an AC system does not cause anything to be emitted except cold air towards the face.