Gas burning car engines explode fuel vapor to push the piston to turn the crank, shaft, wheel. 75% of heat off each explosion goes not to push the piston, but into the engine mass, moving out through the radiator. Not a very successful use of heat, or your expensive fuel. Keep the car tuned up, know what you are buying, some new engines are better now, hybrid and electric may fit a few of us.
In slow, stop and go traffic, about 90% of your fuel is used to accelerate the car, then in a few car lengths or a few blocks, you throw it all away as heat in the brakes. Regenerative coasting and braking can harvest about 50% of this for later use. Look for this in a new car if your shopping. What can we learn from this tiny bit of info? Weight of the car matters, lighter is better, and don't drive to the stop sign, I am amazed at the number of drivers maintaining 40 mpg until braking hard is the only choice.
In faster driving with few stops the cost in fuel is mostly to keep it rolling. The main problem here is wind resistance, aerodynamics. Here most the energy is going to swirl a tube of air behind the car. The cross section, the total area of the car in front view determines the drag. It can be mitigated by round corners and smooth lines, tight seams, clean slick surfaces, but the issue remains, the wider & taller the car the greater the drag. Narrow, low, long, beats fat, tall.
Rolling resistance is the smaller but an important contributor. Tire tread & construction, bearings, drive train mechanical drain, road surface. Drive the smooth road if equal distance, get the car greased, buy low rolling resistance tires if your going to keep the car for the tires life.
Faster X 8. As a general rule most cars increase fuel consumption 8 times to double the speed. 40 to 80 isn't cheap.
Conclusion, Lighter, smaller, slower, fewer miles, more money in your pocket.
Fringe:
ReplyDeleteAnd don't forget to maintain the recommended air pressure in the tires.
Whit
ReplyDeleteYea man, puff em up. Inside your car door it recommends air pressure, this is for riding comfort, on the tire it gives a max. air pressure. Decide for yourself, but I keep mine just a little over the auto manufacturer's value to improve mileage, but well below the max. stated on the tire.
Thanks for reminding me - those bandits at Midas in Evansville owe me a tire rotation.
ReplyDeleteRon
Sarge anonymous, rotate, mark the mothers before you leave it, I caught Sears years ago washing the tires and rolling the car back out. Last time there, and got my money back, may they go broke.
ReplyDeletefringe -
ReplyDeleteI have always wondered why they do not put the same type of mirror found in stock cars on reg road vehicles. It would make the cars more aero friendly and therefore use less gas.........
IG,
ReplyDeleteIt also amazes me that there is not at least a partial covering on the bottom of the car to reduce the violent turbulence under the car. Sure it might add heat and hamper service to have it under the engine, but much of the balance of the undercarriage could have a plastic or metal cowling, the improvement would be noticeable.