On paper it may look like the 2.0-liter engine and six-speed automatic transmission nestled in the otherwise all-new 2020 Hyundai Sonata hybrid’s nose are the same as those in last year’s model. But that’s not the case. Hyundai powertrain engineers rigorously retuned their “Nu” engine and six-speed automatic, and by leveraging the new Sonata’s aerodynamics, too, they’ve advanced the gas-electric sedan’s EPA fuel economy estimates from the back of the midsize hybrid class to the front.
How does 47 mpg in mixed driving sound? That’s only the tip of the 2020 Sonata hybrid’s efficiency spear. The even thriftier “Blue” model pushes that figure to 52 mpg; on the highway, the Sonata hybrid Blue nets a 54-mpg EPA estimate. Per Hyundai, the SEL and Limited trims drop the highway number to as low as 51 mpg. Compare the Sonata hybrid’s 45-50/51-54/47-52 mpg city/highway/combined numbers to the Toyota Camry Hybrid’s 44-51/47-53/46-52 mpg city/highway/combined and the Honda Accord Hybrid’s 48/47/48 mpg rating.
Engine work on the Sonata’s Nu motor for extra efficiency included a higher 14.0:1 compression ratio (up from 13.5:1) and modifications to the combustion chamber that induce more tumble in the intake charge air. The direct fuel-injection system was greatly upgraded, with improved injector spray patterns and a higher 350-bar (5,100-psi) pressure (raised from 250 bar, or 3,600 psi). All of these enhancements allow for a bit more exhaust gas recirculation than before, which reduces pumping losses. Other improvements include an optimized new split cooling system for the block and head, which helps warm critical parts of the engine more quickly, and a variable oil pump to reduce the load on the engine when lubrication needs are low.
While fuel economy has gone up, the four-cylinder engine’s output ratings wiggle down slightly, from 154 to 150 horsepower and from 140 to 139 lb-ft of torque. With the 51-hp/151-lb-ft electric motor carrying over, the combined system rating drops by the same 4 horsepower relative to the 2019 model’s 193 ponies, to 189 .
A new Active Shift Control (ASC) technology uses the electric motor to better synchronize rotational speeds within the transmission, making shifts smoother and faster by up to 30 percent. ASC also is credited with improving both acceleration and fuel economy performance and with reducing friction enough to meaningfully extend transmission life.
The other piece of the efficiency puzzle, the Sonata hybrid’s aerodynamic enhancements, include a unique new front fascia with a “cross-hole” grille pattern and special wind-cheating 16- and 17-inch wheel designs. (Travel-fashionistsas should opt for the 16s because their five V-spokes vaguely resemble Louis Vuitton logos.) There also is a Hybrid-only rear lip spoiler, active front aero flaps to divert surplus air around the engine when cooling isn’t needed, and additional underbody shielding to smooth airflow under there. The result is a claimed 0.24 coefficient of drag (down from the non-Hybrid’s also quite good 0.27), with a 0.05 coefficient of lift. These figures undercut both the Toyota Camry Hybrid (0.25/0.10) and the Honda Accord Hybrid (0.25/0.11)—at least as measured in Hyundai’s wind tunnel.
Revised underbody packaging allows the small high-voltage battery that powers the electric motor to move from beneath the luggage-compartment floor to an area under the rear seat cushion. (The gas tank moves rearward slightly to just behind the battery, beneath the main cushion and backrest.) This helps boost luggage space by 2.5 cubic feet relative to the previous-generation Sonata Hybrid. To assist that battery, Hyundai will offer a solar roof panel capable of generating up to 205 watts of power in full sunlight to add charge and to (separately) maintain the 12-volt starter battery, enabling cabin cooling when parked. The panels are claimed to be capable of adding 3 miles of electrically assisted driving range per day if parked for six hours in bright sunlight.
And finally, improvements in sound deadening help close the gap between the Sonata Hybrid and its Camry/Accord rivals. Hyundai slapped on a new windshield and front door glass that features a three-layer sound-absorbing sandwich construction. Road noise and engine noise at idle and under hard acceleration are now said to be class-competitive; before, they weren’t so much. Other enhancements include a remote self-parking assist feature (amusingly demonstrated in that Bostonian Smaht Pahk Super Bowl commercial), which allows the car to be maneuvered into or out of a perpendicular parking space using the key fob remote, and Hyundai digital key, which uses near-field communications and Bluetooth low-energy technology to enable a phone to function as the vehicle’s key—either permanently or temporarily.
We’re impressed that Hyundai has met or exceeded the fuel economy numbers of the Camry and Accord hybrids, considering that both competitors rely more heavily on their electric motors for motivation and use modern, bespoke hybrid transmissions. Meanwhile, Hyundai continues to sandwich its Sonata’s electric motor between the engine and a conventional automatic transmission, a tried-and-true but hardly cutting-edge arrangement. But hey, careful tuning can yield surprising results …