Hyundai has unveiled the hybrid version of the all-new Sonata sedan in Seoul, Korea, with the model’s highlight being the fuel consumption of 18.2 km/l (5.5 l/100 km or 42.8 mpg US).

Hyundai says the new Sonata Hybrid features a unique hybrid design with an upgraded powertrain that delivers “class-leading” fuel economy. The hybrid system combines a 2.0-liter GDI gasoline engine with a 38 kW (51hp) electric motor. The gasoline engine produces 156PS (154hp) and 190 Nm (140lb-ft) of torque. Compared to the previous model, power and torque are up 4 percent and 5.5 percent respectively.

The electric motor also delivers 8.6 percent improved maximum power, with maximum torque of 205Nm (151lb-ft). The electric motor is fed by a lithium-polymer battery pack with a capacity of 1.62 kWh, 13.3 percent higher than the previous model’s 1.43 kWh. The battery has been relocated under the floor of the trunk, allowing for a flat trunk floor. Thanks to this, Hyundai says the cargo area is more usable and 10.5 percent larger.

The gasoline engine sends power to the road via a six-speed automatic transmission. The gearbox is fitted with a traction motor, while the torque converter has been removed. A lighter torsion damper, and new engine clutch with fewer clutch discs reduce drag and contribute to a more efficient transfer and use of power.

The Korean automaker says it has invested 27 months and approximately 180 billion Won ($164 million) in the development of the new Sonata Hybrid. The model will launch in major markets outside Korea from the first half of 2015, with Hyundai targeting 55,000 sales for next year: 18,000 in Korea and 37,000 overseas. The US-spec model will debut at the Detroit Auto Show next month.

The new Hyundai Sonata Hybrid will also spawn a plug-in hybrid variant next year, which will be Hyundai’s first ever PHEV. The carmaker also plans to introduce its first dedicated hybrid model in the second half next year.

Hyundai picked this year’s North American International Auto Show to launch its first-ever plug-in electric vehicle, the 2016 Sonata PHEV, which will go on sale later this year in select markets.

The PHEV (Plug-in Hybrid Electric Vehicle) version of the Sonata features a 9.8 kWh lithium polymer battery pack that’s nearly five times larger than that of the Sonata Hybrid. It is also expected to provide an all-electric range of 22 miles (35 km), more than any other mid-size PHEV.

The Transmission-Mounted Electrical Device (TMED) is a 50 kW electric motor that’s used in place of a torque converter and is 32 percent more powerful than the one in the Sonata Hybrid, allowing for all-electric operation at higher speeds.

The internal combustion engine is the same 2.0-liter four-cylinder GDI direct injection petrol unit that’s also used in the Sonata Hybrid. It puts out 154hp and 140 lb-ft of torque and is mated to a six-speed automatic transmission. Total output of the Sonata PHEV is 202hp at 6,000 rpm.

Hyundai claims that, based on internal estimates, the Sonata PHEV will deliver 93 MPGe combined in EV mode, and 38/43/40 mpg city/highway/combined in charge sustaining mode. Recharging takes from two and a half hours using a 240V charging station to five hours via a standard 120V power outlet.

Like the Sonata Hybrid, the PHEV version boasts the same design changes to not just differentiate them from the conventional models but, more importantly, lower the drag coefficient to a class-leading Cd of 0.24.

The Sonata PHEV stands out thanks to the charging port on the driver’s side front fender, a unique grille, front and rear bumpers, front and rear lights, chrome sill, new wheels and Hybrid logos. It will also be available in two exclusive colors, Graphite Blue Pearl and Seaport Mist.

Owners will be able to monitor and manage the Sonata PHEV remotely via the Blue Link smartphone app, which allows them to select when to stop or start charging and set up a charging schedule during the week, even setting the time frame of their choice.