New Ways Carmakers Are Getting You More MPG

Although most automakers say all-electric vehicles are the future, their engineers also have been busy making fuel-efficiency improvements to the gasoline-powered cars, SUVs, and trucks that most U.S. drivers still rely on. For a variety of reasons, such as consumer demand and government fuel and emissions standards, automakers have been forced to invent gas-saving innovations as they try to squeeze out incremental improvements to fuel economy.

Consumers shopping for new cars now face a hodgepodge of these innovations, such as gasoline direct fuel injection, automatic transmissions with more gear ratios, turbocharged engines, and stop/start systems that shut off the engine instead of allowing it to idle. Few of these technologies significantly increase fuel efficiency or reduce tailpipe emissions on their own, but working together they can have a cumulative effect.

To help car shoppers navigate these fuel-saving features, CR talked with manufacturers, experts, and consumers to find out exactly how each technology works, and combined those insights with observations from our own testers, who have evaluated these features in real-world driving conditions. We’ve found that some of these technologies, such as turbocharged engines, can end up compromising drivability and sometimes cause reliability problems.

“There are no free rides in this business,” says Gabe Shenhar, associate director of CR’s auto test program. “Drivers might find the stop/start annoying, or turbo lag could make a car hesitant to accelerate. Aerodynamic styling might result in a lower, curvier car that compromises visibility and ease of access.”

Through our dynamic ratings chart, you can discover which vehicles deliver the most miles per gallon. Below, you can learn the benefits of each gas-saving technology, as well as any potential drawbacks. You can arm yourself with this information as you shop for a new or used vehicle.

Most of the highest-mpg vehicles we highlight are hybrids—meaning they combine internal combustion engines and electric motors to save fuel. Most also have electronic continuously variable transmissions (eCVTs), which can save energy by regulating engine speed. A few of the models on our list have traditional gas-powered engines and achieve strong fuel economy without using hybrid technology.

We do not highlight any battery-only electric vehicles, called EVs, because they don’t use any gasoline and currently represent only a sliver of the U.S. new-car market. Diesel-powered cars also get good fuel economy, but they’re not on our list because they’re not necessarily cleaner burning, and the selection among U.S. passenger vehicles has dwindled.

The newest gas-saving innovations, taken together, have made it possible for a pickup truck to achieve highway fuel economy in the mid-20s, to say nothing of the many SUVs and cars that now push into the 30-plus mpg range. The gains have shown up across the board: According to the Environmental Protection Agency, average fuel efficiency for new cars in the U.S. improved to a record 25.1 mpg in 2018 and was projected to reach 25.5 mpg in 2019. In the process, automakers also have decreased harmful tailpipe emissions by about 1.7 percent—a new low that has environmental and public health benefits.

“When car manufacturers report an increase in mpg, it’s due to the collective use of multiple technologies,” says Bassem Ramadan, PhD, head of the mechanical engineering department at Kettering University in Flint, Mich. “There is no single technology that is or will be the silver bullet that will dramatically improve fuel efficiency and reduce emissions at the same time.”

What About EVs?

So why all this innovation with gas-powered engines even though electric vehicles clearly outperform all gas-powered cars when it comes to energy efficiency? The case for them is strong: EVs use no gasoline and emit zero tailpipe emissions. They can be quick and very satisfying to drive. And an exclusive CR analysis shows big savings on maintenance and operating costs over time when compared with traditional gasoline-powered vehicles. (See “EVs Offer Big Savings Over Gas-Powered Vehicles.”)

The answer is that EVs are not yet a solution for many drivers and are up against several obstacles that so far have held back wider adoption: long charging times, limited (but ever-increasing) battery range, and larger price tags. So far, there hasn’t been much market demand for EVs, which—along with plug-in hybrids—accounted for less than 2 percent of U.S. vehicle sales last year, despite the increasing popularity of the technology.

“Automakers have been slow to build EVs in part because, until recently, battery costs have been quite high,” says Chris Harto, senior transportation policy analyst at CR. “That is rapidly changing. Expect to see a lot more compelling EVs over the next few years.”

Based on a flurry of automaker announcements, it’s clear that the industry has plans to move toward more electric models. For example, BMW and Mercedes-Benz—leaders in automotive research and development—say they plan to reach 50 percent electrification across their lineups by 2030. And certain other brands, such as Volvo, have pledged to eventually have an EV option for every model they offer. Some newer automakers—notably Tesla—offer only EVs.

At the same time, Tesla and other companies have been building out national public charging networks, with a growing number of DC fast-charging stations that can make on-the-road charging more palatable for drivers.

As of 2019, there were almost 27,000 public and private charging-station locations across the U.S., with more than 85,000 outlets—about double the numbers from 2015, according to the federal Alternative Fuels Data Center. Depending on the battery and charging equipment, DC fast-chargers can add 60 to 80 miles to EV range in 20 minutes, about the time it takes to eat a quick meal on the road.

“The reality is that most of the effort on internal combustion engines is starting to wind down in favor of electric development,” says Sam Abuelsamid, principal research analyst at Guidehouse Insights, a market research firm. “Much of the restructuring we’ve seen at automakers and suppliers in the last few years has involved getting rid of engineers with engine expertise in favor of more software and electrical engineers. That’s where all the major action is today.”

Fuel-Saving Tech

CR's experts highlight key gas-saving innovations you might find in your next car. They explain how each works, along with the potential drawbacks for your driving experience.

8-, 9- & 10-Speed Automatic Transmissions

A wider array of gears reduces engine speed during highway driving to improve efficiency and save fuel. This also can provide quicker acceleration.

Potential drawbacks: In some cases, downshifting can feel slow, and frequent shifting at lower speeds can feel clunky.

Active Grille
Shutters

These devices close off a portion of the grille opening and create fuel efficiency by improving aerodynamics and balancing engine cooling needs. They also help the engine warm up more quickly.

Potential drawbacks: Added complexity could affect reliability.

Aerodynamics

Sleeker body designs that reduce drag can improve fuel economy. Sedans are usually more aerodynamic than large, boxy SUVs and trucks. Improvements in this area can result in less wind noise and sleeker, sportier designs.

Potential drawbacks: Rakish styling can squeeze interior space and impede visibility.

Continuously Variable Transmission (CVT)

Replaces traditional transmission gears with a setup that makes continuous adjustments to the “gear” ratio, smoothing operation and keeping the engine at optimal operating speed.

Potential drawbacks: More pronounced engine noise.

Cylinder
Deactivation

Cuts off the fuel supply to specific cylinders when full engine power is not required, improving fuel economy for larger engines.

Potential drawbacks: Some early systems can have mild vibrations when cylinders activate or deactivate.

Electric
Steering

A small electric motor provides power assist to the steering mechanism in place of an engine-driven hydraulic pump. Reduced load on the engine brings down fuel consumption by about 5 percent.

Potential drawbacks: Reduced steering feedback can diminish road feel.

Low-Rolling-Resistance Tires

Special rubber compounds and tread designs can reduce the friction generated from a rolling tire, reducing the energy needed to drive the car forward.

Potential drawbacks: The compounds in these tires can increase wet stopping distances.

Regenerative Braking

Found on hybrid and electric vehicles, this system converts energy from braking and coasting into electricity, which can help recharge the battery. This provides increased electric range and fuel economy (on hybrids).

Potential drawbacks: The system can affect coasting ability and brake pedal feel.

Stop/Start

The feature saves fuel by automatically shutting off the engine when the vehicle comes to a stop to avoid excessive idling at red lights or in standstill traffic. The engine restarts automatically.

Potential drawbacks: Can cause hesitation and shudder on restart, and compromise the performance of A/C and other accessories during shutdown.

Active Grille Shutters
The shutters depicted in the close-up image are closed during driving to save fuel by improving aerodynamics.

Continuously Variable Transmission (CVT)
The steel teeth in the image below are part of a special belt that expands and contracts in a CVT to replace traditional gear-shifting.

Fuel Economy Revolution

Most vehicles sold in the U.S. are still powered by gasoline internal combustion engines—with turbocharged models on the rise—but that is changing as more gas-electric hybrids, plug-in hybrids, and battery electrics hit the market. Here are the various technologies under the hoods of today’s most efficient vehicles.

Small-Displacement Turbo Engine

Turbocharging boosts power by pushing more air in, allowing the engine to burn more fuel. This generates more power from a given engine size, giving on-demand acceleration and improved fuel economy under a light load.

Potential drawback: Uneven acceleration, or turbo lag, when starting out.

Mild Hybrid

Provides some electric assist to a traditional gas-powered engine but does not provide electric-only driving. The system smooths out the stop/start feature by keeping accessories running when the engine shuts down to save fuel.

Potential drawback: The name might suggest more fuel economy gains than these cars can deliver.

Hybrid

Combines a combustion engine with an electric motor (or motors) to improve fuel economy. The engine, along with braking and coasting, automatically recharges the battery. These systems typically provide minimal electric-only driving.

Potential drawback: Added weight and mechanical complexity.

Plug-In Hybrid

Like a hybrid, but it has a larger battery and increased range with electric-only driving, significantly reducing fuel consumption for daily trips if charged often. The battery is recharged by plugging the car into an outlet.

Potential drawback: Added weight, and large battery can steal cargo space. Need to frequently charge to get full benefit.

Electric (EV)

A high-voltage electric motor—or multiple motors—replaces the combustion engine for propulsion, and a rechargeable battery replaces the gas tank. EVs don’t use any gasoline, and they operate quietly and cost less to run.

Potential drawback: Shorter range compared with a gas-powered car, and long charging times.

Editor's Note: This article also appeared in the November 2020 issue of Consumer Reports magazine.

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