Although the U.S. government is pushing automakers toward nearly doubling average fuel economy by 2025, the automakers are loath to abandon their massive investments in internal combustion engines. To help, they are turning to technologies from hybrid and electric cars to find ways to improve fuel efficiency in their gas cars. And they are finding them.
Hybrids and EVs were developed primarily to reduce the use of gasoline, and to make that happen, engineers had to come up with substantial leaps in efficiency technologies on several fronts, including weight reduction, friction reduction, aerodynamic improvements and new systems to create or conserve power.
Now, with several million hybrids and tens of thousands of electric cars on the road, automakers are recognizing that they can apply some of those improvements to conventional vehicles to help achieve various national efficiency goals.
The National Academy of Sciences says at least 80 percent of the energy in a conventional vehicle's gas tank is wasted through thermal, friction and idling losses in the engine and exhaust system. Anything that can be done to cut those losses ends up improving fuel efficiency.
So from "micro-hybrid" stop-start systems and eco-driving coaching guides to electrically assisted brakes and reduced-friction tires, many of the tweaks that help give hybrids and EVs their world-class fuel economy may soon be found on conventional cars and trucks.
Here's a look at some of the technologies that conventional internal combustion vehicles are — or soon will be — adapting from hybrid and electric cars.
Auto Stop-Start Systems
The best way to improve fuel economy is not to burn fuel, and that's where auto stop-start systems can help. A standard part of every hybrid car system, auto stop-start automatically shuts down a vehicle's engine at idle and immediately restarts it when the driver presses the accelerator or lifts off the brake or clutch pedals.
In hybrid cars, however, large and expensive nickel-metal hydride or lithium-ion batteries provide all the juice a stop-start system needs to do its job. Engineers who looked at migrating auto stop-start systems to conventional vehicles first had to figure out how to make them work with small lead-acid batteries at a lower cost.
An advanced high-power lead-acid battery called an absorbed glass mat battery proved to be the answer. Johnson Controls, a major global supplier of those batteries, estimates that up to 40 percent of all new cars and light trucks sold in the U.S. in 2015 could be equipped with auto stop-start systems.
Used in conventional cars and trucks, stop-start systems can cut combined city-highway fuel consumption and greenhouse gas emissions by 3-10 percent. By eliminating engine idling, stop-start systems also reduce toxic and smog-causing tailpipe emissions. The systems deliver their fuel economy improvements in city situations that involve lots of stop-and-go driving. And they can do it at relatively little cost to the consumer. Ford Motor Company, for instance, recently announced a stop-start option on its 2013 Fusion for just $295.
Electric cars and some hybrid vehicles don't develop the engine vacuum needed to activate the hydraulic brake systems used on conventional cars and trucks, so carmakers developed electrically triggered hydraulic braking systems.
In a conventional all-hydraulic setup, the vacuum created by the internal combustion engine augments the force needed to push the hydraulic fluid through the brake lines to activate the brakes at each wheel.
Electrohydraulic systems use electric motors to compensate for the lack of vacuum boost. When the driver applies the brake pedal, that triggers the motors, which in turn power the piston in the brake master cylinder, pushing brake fluid through the brake lines.
The fuel-efficiency benefit of electrohydraulic brake systems is that they weigh less than conventional hydraulic systems, by as much as 7 pounds. It's not a lot by itself, but can be a key ingredient in a particular car model's overall weight-loss plan. Automakers see vehicle weight reduction as an important piece of the fuel-efficiency improvement strategy: Every 100 pounds a car or truck sheds can boost fuel economy by 1-2 percent.
TRW Automotive, which supplied the technology for GM's hybrid pickups and SUVs beginning in 2007, expects electrohydraulic brakes to start showing up on conventional vehicles by 2016. Continental AG, which makes the electrohydraulic brake systems used on Ford's Escape and Fusion hybrid cars, says it has contracts from three other major automakers to develop systems for conventional cars and trucks.
In addition to their weight-reduction benefit, electromechanical brakes offer a potentially important safety feature. They activate more rapidly than conventional brakes, giving a vehicle's onboard computer valuable milliseconds to calculate the likelihood of a crash and activate other active safety systems.
Automotive aerodynamics is not strictly a hybrid and EV technology. But the advent of those highly efficient cars has given birth to advances in aerodynamics that once were considered too expensive for everyday car models.
These technologies include active aerodynamics such as motorized grille shutters that close down a vehicle's grille openings at higher speeds to improve airflow and reduce fuel-draining drag.
Other improvements that are being used in the mainstream after widespread use in the hybrid and electric car markets are fully sealed underbodies, squared-off rear ends and airflow diverters. The latter often are small fins, placed under bumpers or designed into headlamp housings, that keep the air flowing smoothly over and around the moving vehicle to prevent drag-inducing turbulence from forming.
Expect to see more of the aerodynamic techniques that were perfected for EVs and hybrids come into use on all kinds of cars and trucks, says Christopher Chapman, chief designer at Hyundai Design North America.
Hybrid and electric cars make some of their own energy through a process called regenerative braking, in which a car's electric motors switch polarity and act as a generator when the driver applies the brake pedal or releases throttle pressure.
Conventional cars and trucks don't have the big batteries and electric motors found in hybrid cars, but engineers recently have figured out several ways to use a vehicle's braking energy to cut fuel consumption.
In this case, regenerative braking systems turn the vehicle's alternator into a generator when the driver applies the brakes or lifts the throttle. They use the electricity the alternator makes to recharge the 12-volt battery or, in some cases, to charge a capacitor, which is a storage device that can hold power and release it very quickly.
Hybrids and EVs use power from their regenerative braking systems to run their electric motors. Conventional cars and trucks use them to power greedy onboard electronics, including headlamps, taillights, interior lights, the instrument panel and the audio and infotainment systems.
It can take up to 10 horsepower to run an alternator off a car's engine, so the use of a regenerative braking system that reduces or eliminates that parasitic drain can boost fuel efficiency by 5 percent or more.
A vehicle spends about a third of its energy consumption to overcome friction in the engine, in its other mechanical parts and from the tires rolling over the road. Tire friction alone accounts for as much as 15 percent of a passenger vehicle's fuel consumption, according to the federal Department of Energy.
So it stands to reason that reducing that friction, which is also known as "rolling resistance," helps improve fuel economy.
Carmakers and tire companies perfected low-rolling-resistance tires for hybrids and EVs, vehicles in which every ounce of gasoline or watt of electrical energy matters. But it didn't take long for automakers to understand that if reduced-resistance tires worked to help hybrids save gas, then surely they'd work equally well on conventional cars.
These days, most new cars come standard with low-rolling-resistance tires, which can improve fuel efficiency by 1.5-4.5 percent, depending on the tires' degree of resistance reduction.
Consumers can ensure consistent fuel-efficiency from their aging vehicles by always replacing the standard tires with tires of equal — or less — rolling resistance. Most tire manufacturers offer one or more low-rolling-resistance brands, and rolling resistance information is available from tire sellers.
Driver Coaching Displays
Green trees, leafy vines and other "green" icons first showed up on hybrid cars' instrument panels to tell drivers whether they were doing a good job of applying efficiency techniques such as steady, controlled acceleration, downhill coasting and avoidance of quick starts.
Automakers learned from hybrid owners that driver coaching tools really can work to help efficiency-seeking drivers overcome fuel-wasting techniques. Ford Motor Company, for instance, claims that its EcoMode feature, which rates and rewards fuel-efficient driving by displaying green leaves on the instrument panel, can improve fuel efficiency by as much as 20 percent.
Now coaching displays are starting to show up in conventional vehicles. Ford makes them standard on the Focus lineup. Hyundai makes its BlueLink telematics system, with an EcoGuide feature, available on five non-hybrid models.
Eco Route Planning
Another tool that first was developed for electric and hybrid vehicles and now is being pushed to conventional cars and trucks is the mapping of the most fuel-efficient routes.
Such systems use the vehicle's navigation system or a smartphone application to show routes that not only are the fastest, most scenic or freeway-free but that minimize hill climbing and avoid traffic congestion to provide the most fuel-efficient way from one place to another.
BMW, which offers the eco-mapping function on all of its models, also is working on upgrades that will coordinate with so-called intelligent traffic systems as various cities install them. One version would communicate with traffic signals to predict when lights will change.
"That will allow the car to tell drivers when to alter their speed so they can avoid stopping at red lights, which is a big waste of fuel," says Dirk Rossberg, head of BMW's U.S. technology office in California's Silicon Valley.
It All Adds Up
Used alone, none of the technologies being transferred from hybrids and electric cars to conventional gas burners can deliver a substantial gain in fuel economy.
But when they're bundled, these features can help keep cars and trucks with internal combustion engines competitive in the race for improved fuel economy. They're especially effective when they're combined with other efficiency-increasing technologies, such as downsized engines and the lightweight, super-strong alloys and composites used in body and frame construction.
These technologies and features are just the start of the auto industry's effort to harvest fuel-saving ideas from its most efficient vehicles.
"There's a lot more coming," says Larry Nitz, head of GM's vehicle electrification program.