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The cherry on top of the Hyundai Sonata Hybrid sundae, according to most reviewers, is the price. Starting at about $26,000, the Sonata Hybrid costs less than the Ford Fusion Hybrid, Toyota Camry Hybrid, and Nissan Altima Hybrid.

Reviewers have a hard time finding anything to complain about on the Hyundai Sonata Hybrid. If you like everything about the Sonata Hybrid except its price, consider one of the gas-only Sonata models. The Sonata starts at just over $19,000 and comes with the same standard interior features as the Sonata Hybrid. The Sonata Hybrid is most often compared to the Ford Fusion Hybrid, Toyota Camry Hybrid and Nissan Altima Hybrid. Also, most reviewers say that the Sonata is the best affordable hybrid sedan option out there.

Hyundai joins that second group with its first hybrid, which is based on the Sonata sedan.

What exactly does the "Sonata Hybrid" have that will distance it from the Camry and Fusion hybrids? Hybrid-ness
Before I get into the performance and technology aspects of what makes the Sonata Hybrid tick, I've got to point out the fact that the Sonata Hybrid looks dramatically different from its gasoline-only sibling. The Sonata has a lower coefficient of drag than its competition, at 0.25 Cd versus the Camry Hybrid's 0.27 Cd and the Fusion Hybrid's 0.33 Cd.

Inside, all Sonata Hybrids get a digital readout between twin analog gauges that shows hybrid performance and trip computer information. Mileage is rated at 36/40 mpg city/highway, which outdoes the 2011 Camry Hybrid's 31/35 mpg rating and bests the Fusion Hybrid in highway mileage; the Ford is rated 41/36 mpg.

The Sonata Hybrid has 10.7 cubic feet of trunk space, while the base four-cylinder model has 16.4 cubic feet. The Sonata Hybrid's six-speed automatic transmission is also a hybrid first. Hybrids typically use continuously variable automatic transmissions to maximize fuel efficiency. When the Sonata Hybrid isn't in that fuel-sipping mode, shifts are crisp and acceleration is strong. My test drive took me through Southern California mountains, and the hybrid drivetrain performed well. The hybrid's handling and ride quality are both on the soft side, like the base Sonata.

Before hybrid buyers scoff at these seemingly low figures, I'll say that these numbers should be considered the bottom of the Sonata Hybrid's mileage spectrum. Sonata Hybrid in the Market
Hyundai's first hybrid is impressive in almost every way.
Now, Hyundai has introduced a hybrid version of the Sonata that delivers excellent mileage and can be driven in zero-emissions, full-electric mode at speeds up to 62 mph.

The Sonata Hybrid incorporates Hyundai's latest Hybrid Blue Drive system.

The new hybrid system combines the lithium-polymer battery with an electronically controlled clutch arrangement to create a full hybrid that can use an existing six-speed automatic transmission. In the Sonata Hybrid, Hyundai claims to have built its system around a battery that leapfrogs existing battery packs. We wouldn't call it a breakthrough—after all, the Nissan Leaf and Chevy Volt will arrive with lithium-ion batteries that use a different chemistry than the Hyundai, but the Sonata's hybrid's batteries are a significant step compared to what's used on existing hybrids.

Compared to nickel-metal-hydride batteries of the same output, such as those used in the hybrid versions of the Toyota Camry and the Ford Fusion, the lithium-polymer batteries are 35 percent lighter and 40 percent smaller.

Compared to lithium-ion batteries, such as those used in electronic appliances, lithium-polymer batteries offer a similar energy density but with lower heat generation, which improves cycle life.

Mercedes-Benz was first to introduce similar lithium-ion batteries a year ago in its S-400 Hybrid luxury sedan using a small battery pack to assist a 20-hp motor in a "mild" hybrid that was not designed to operate on electric power alone.

The lithium-polymer batteries in the Sonata use a manganese spinel chemistry that balances energy density with thermal stability. This greater thermal stability extends battery life.

Hyundai engineers say that the lithium-polymer batteries can tolerate tens of thousands of charge cycles, without having to use a liquid-cooling system. The batteries cost about the same to produce as lithium-ion batteries, but are perhaps 10 to 15 percent more costly than nickel-metal-hydride batteries.

The Sonata Hybrid is unusual in that Hyundai engineers expect the car to get better highway mileage than city mileage.

The Sonata Hybrid shares the same fluid body panels with all other 2011 Sonatas but has lighter, more aerodynamic pieces at the front and rear.

Also enhancing highway mileage is an Atkinson-cycle version of the 2.4 Theta II engine, based on the standard 2.4-liter engine in the Sonata, but recalibrated to run on the Atkinson cycle, a common way of improving the efficiency of engines used in hybrids. Combined, the engine and electric motor generate 209 hp and 195 lb-ft of torque, compared to 198 hp/184 lb-ft from the 2.4-liter version standard in the Sonata.

The multi-disc clutch pack sits within the motor and is used to decouple the 2.4-liter engine for idle/stop and electric-drive modes. By allowing higher EV-only speeds, the clutch plays a big part in the Sonata's highway fuel efficiency. With a 17.2-gallon fuel tank, the Sonata Hybrid has a theoretical



With a light throttle foot and a full battery charge, it's possible to get the car up to highway speed before the engine kicks in. We did notice a transition between engine and motor assist as we powered onto the proving grounds' high-speed oval at full throttle, but it's an acceptably seamless power delivery, all things considered, and better than some two-motor hybrids we've driven.

Braking, always a little strange in hybrid vehicles, is also close to ideal in the Sonata. It feels just like any other car with four-wheel disc brakes and four-channel ABS. Light braking regenerates the battery pack.

On the handling course, where shifting, downshifting and hard acceleration were required, the Hybrid Sonata spent most of its time with the engine running, driving like a normal family sedan. Overall, it's the most spirited midsize hybrid we've driven.