NEW YORK – Tuning and logic changes boost horsepower and produce a 6% fuel-economy increase in the ’13 Hyundai Sonata hybrid that recently went on sale, the auto maker says.

Car buyers will get these improvements for $200 less than the ’12 model, while continuing to receive a lifetime battery-pack warranty.

The price for the base hybrid model starts at $25,650 and climbs to $30,550 for the top-of-the-line Limited model. A $795 delivery cost is extra.

The ’13 model's Blue Drive powertrain features a bigger-capacity 10.5-kW starter generator, 35-kW (47-hp) electric motor, compared with 30-kW in 2012, and a 47-kW (compared with 34-kW) LG Chem 72-cell lithium-polymer battery pack. The more-powerful electric motor also helps the system capture more energy during regenerative braking.

These components are mated to a 2.4L 4-cyl. engine running on an Atkinson cycle. Overall power totals 206 hp. The setup increases electric-only driving range to just under 2 miles (3 km), says John Y. Shon, manager-product planning.

A top speed of 72 mph (116 km/h) can be achieved on battery power alone during acceleration, but Shon admits it's difficult to measure because of when the transmission clutch engages and shifts to using power from the internal-combustion engine.

Changeovers to battery power can occur at any cruising speed in the hybrid, whether the vehicle is traveling 70 mph (133 km/h) or at half that speed. It depends on the charge in the battery pack, but for the most part the vehicle operates on battery power at startup from a stopped position, as do other hybrids.

The transition from battery to ICE power is transparent. There are no abrupt gear changes felt during a short test drive here. The lack of road and wind noise provide an altogether quiet ride in the hybrid vehicle.

Fuel economy in the ’13 Sonata hybrid is estimated at 36/40 mpg (6.5-5.9 L/100 km) city/highway and a combined 38 mpg (6.2 L/100 km) in the base model. Combined fuel economy in the Limited model is 37 mpg (6.4 L/100 km).

Conventional Sonatas are produced at Hyundai's plant in Montgomery, AL, while all hybrids are imported from the auto maker’s Asan factory near Seoul, Korea.