Compare Types of Efficient Car Technologies


In the mid 2000s, and through 2015 a new generation of diesel vehicles was touted as offering lower emissions, high efficiency, and superior performance. In ways this was true, but a cheating scandal by VW and others set in motion public backlash away from diesels. Diesels are yet extremely thermally efficient, can be made clean, do get high mpg compared to gas engines, and still have their advocates.

E85 Ethanol

A growing number of vehicles can run on an 85 percent blend of ethanol. The absolute value of ethanol blends has also been contested. It is one approach begun last decade that is much less prominent than electrification such as by hybrids, plug-in hybrids, and pure battery electric tech, but overall plays into the mix of attempting to reduce petroleum usage.


Pure electric cars rely on lithium-ion batteries either in a subfloor layer, or stuffed under the rear seat in back of the vehicle. They are the most energy efficient vehicles widely available and the industry is fast going in their direction due to costs coming down and their ability to meet increasingly stringent emissions regulations. Prices are still higher than for other tech, but tax credits, subsidies, inexpensive lease deals, and reduced energy costs can offset the difference.


Today’s gas-electric hybrids are the among the most fuel efficient and greenest cars among vehicles relying on internal combustion power. Plug-in hybrids build on the same principle of merging gas-plus-electric motive power, and all-electrics require no fuel, but hybrids remain popular. This is because they require consumers to do nothing different in terms of fueling their vehicles. They have no plug, and tend to cost less, albeit are no longer eligible for tax credits and subsidies.


Hydrogen fuel cell vehicles (FCVs) are a form of all-electric hybrid merging a fuel cell stack with a traction battery. They emit nothing but water and drive like battery electric vehicles. FCVs are for now confined to markets in California and infrastructure is scarce. Manufacturers are betting by the 2020s and beyond they will catch up, but battery electric cars can be recharged anywhere now, while their costs are also coming down. The two approaches also compete for mind share, and battery electrics are more popular, though with hope of sustainable hydrogen in the future, FCVs have strong advocates.

Plug-in Hybrid

Plug-in hybrids were introduced for the 2011 model year with the "extended-range electric" Chevrolet Volt and since then numerous manufacturers have emulated the formula of adding a big battery to a hybrid powertrain for part-time EV driving. They are a way for manufacturers to meet emissions regulations, and drivers may radically reduce day to day fuel consumption and emissions, while having full flexibility (no "range anxiety") to travel far with gas fill ups. A federal tax credit from $2,500-$7,500 is available depending on battery size, as are varying subsidies in many states.

Small Car

The oldest strategy to reduce fuel consumption is to downsize. Smaller vehicles can do the job while getting mpg in the high 30s, even low 40s in a couple cases. They do not return mpg in the 50s or beyond that the best hybrids or plug-in hybrids do, and don't come close to pure EVs, but they cost much less. Prices in the teens and lower 20s make them expedient fuel misers. For those wishing to save some fuel and emissions, and on a limited budget, small cars are a solution worth exploring.


A stop-start system is a simple way to aid efficiency. Automakers are putting this technology not only in gas-electric hybrids, but even straight internal combustion vehicles to save fuel. Essentially, the vehicle shuts its engine off at a stop, such as at a traffic light, or stop sign, and a powerful starter enables the engine to immediately come back on when it's time to move again. Fuel consumption and emissions are thus reduced due to the engine not running for several seconds up to a couple minutes or longer.

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