Best Mileage Cars - features and characteristics
From simple weight reduction to complex regenerative braking, todays best mileage cars boast many different fuel saving features and characteristics.The first characteristic of the most economical cars is their size. None of them are large cars. Although they do vary in size from tiny city cars to mid sized family cars, you won't find a two tonne car breaking any fuel efficiency records. With less weight to carry around smaller cars require less energy and manufacturers have taken this a step further by using lighter materials for some car parts. The Smart Fortwo for instance uses many plastic body panels and weighs just 730kg.
Overcoming wind resistance and rolling resistance requires lots of energy and small improvements here can translate into vastly improved fuel mileage. Manufacturers pay great attention to lowering the drag coefficient of their vehicles and the best mileage cars feature some of the lowest coefficients around. When designing body shapes there's usually a trade off between aerodynamics and cabin space - for example manufacturers need to be aware of providing enough headroom for rear passengers - but even a simple grill redesign can significantly reduce wind resistance. Toyota's Prius has a drag coefficient of 0.25. By comparison the average drag coefficient of an SUV is 0.42.
Fuel efficient cars tend to have narrower wheels with less rubber in contact with the road. However, low rolling resistance tyres are increasingly being installed which take this a step further through the use of specialist compounds which reduce the friction between the internal molecules in the rubber.
Today's crop of economical vehicles tend to feature either small diesel or petrol electric hybrid powerplants. Efficient diesel engines are characterised by their small size often with only 3 cylinders, common rail design, variable valve timing and turbochargers. These all contribute to maximum efficiency while maintaining a practical amount of power.
Petrol electric hybrids tend to have slightly larger engines than the diesels and the best performers have the most powerful electric motors. Unlike the mild hybrids these hybrids are capable of powering themselves through the use of their electric motor alone in city traffic. They also feature regenerative braking, which recaptures some energy that would otherwise be lost through the use of the brakes.
Efficiencies are also gained in a vehicle's transmission system. Either extra long gear ratios are used for the highest gear, meaning that the engine doesn't need to revolve as fast to turn the wheels, or a continuously variable system is used. Continuously variable transmission, or CVT, comprises of a cone shaped gear instead of individual gear cogs. The idea is that the cone shape provides a limitless number of gear ratios enabling the engine to run at its most efficient speed no matter how fast the car is going.
Originally developed for hybrids but now incorporated into many non-hybrid eco cars are start stop systems. This enhancement allows the engine to automatically cut out and restart when stopped in city traffic. A simple concept which has the ability to save lots of fuel in busy rush hour traffic.
The above are common characteristics of todays most fuel efficient cars but new technology is being developed all the time, such as turbosteamers and laser ignition. Since green cars are the industry's biggest growth area at the moment a lot of money is being poured into research so we can expect new features to appear quite regularly.
Todays top performing cars for economy can return fuel mileage figures in excess of 60 mpg. Besides saving you a lot of money they are also surprisingly nice to drive. Many of them don't feel as small as they actually are to drive. They often handle very well and have the feel of a large car. Some of the midsize cars have plenty of room for 4 passengers and can fit 5 passengers if required.
With all their high tech features, the best mileage cars are not the cheapest out there, however the diesels in particular are very competitively priced. As the cost to produce batteries goes down so too will the price of hybrids.
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