UPDATE: This story was changed to reflect updated EPA mileage estimates.

new Prius

Photo courtesy of Toyota.

Toyota’s newest hybrid is almost here. Last week, the car company invited a group of journalists and bloggers to the third generation Prius preview in Napa, Calif. The deal was we could road test the 2010 model to our heart’s content, but we needed to stay mum about our impressions of the car and mileage readings until the end of March. Sigh.

So I have been figuratively bound and gagged, but the Toyota folks did provide more detailed technical specs than those announced in January at the Detroit Auto Show. Green features of note:

Mileage: In January, the figure Toyota touted was 50 mpg, which is confirmed by EPA roadtests (51 city/48 highway/50 combined). Counterintuitively, the larger 1.8 liter engine in the 2010 Prius is responsible for more efficient highway mileage. Chris Risdon, Toyota’s senior product education and development administrator, explained that the larger engine creates more torque so it can turn at a lower rpm at higher speeds and consequently use less fuel.

Solar panel: The promise of the rooftop solar panel doesn’t live up to January’s expectations.

Solar panel with moonroof Solar panel with moonroof Photo courtesy of Toyota.For starters, it’s only an “available package” as opposed to a standard feature. But here’s the real punchline: the panels only power the ventilation system when the car is turned off. So when parked in the direct sunlight, the ventilation system draws on solar power to circulate cool air through the car. Otherwise, the power generated from solar panel goes to waste because it’s not wired to the main battery.

Prius chief engineer Akihiko Otsuka hinted that Toyota may try to do more with linking solar generation to the car’s power system in the future, but at present, ignoring the aftermarket potential, the new solar panel is more symbolic than functional.

Driving modes: Unlike the second generation Prius, there are three alternative driving modes in the 2010 Prius: EV, Eco, and PWR. Subject to the charge of the battery, EV mode runs purely off the battery for about 1/2 mile under 25 mph. Eco mode smooths out the electronic throttle control (for car nerds, it sets the throttle opening to a max of 11.6 percent) and reduces the air conditioning to maximize fuel efficiency. And the least green option, PWR mode throws more juice at the engine when you want pull-out from a stop or haul a hummer.

Hybrid Synergy drive displayHybrid system indicatorPhoto courtesy of Toyota.Multi-information Display: Toyota overhauled the driver information display and pulled it out of the Navigation panel (thank goodness) and up onto the dash. Coming standard in every 2010 Prius, there’s now a five-inch wide digital display that toggles between the energy monitor, hybrid system indicator, fuel consumption record, and trip information. The driver can always see mileage, average speed, and distance traveled, and when driving most efficiently, a little green “eco flag” pops up to reward green driving behavior.

Ecological plastics: The driver’s seat and some of the scuffs and trims are made from castor-oil derived plastics from Canada, according to Otsuka. A Toyota Lifecycle Assessment pegs that the use of this plastics emits 20 percent less CO2 then their petroleum-derived brethren, but there was no word as to exactly what factors were weighed when determining that statistic.

Battery: Otsuka referred to the 2010 Prius powertrain as “90 percent new, and 10 percent the same,” but it’s worth noting that the 10 percent that stayed the same is essentially just the battery. Toyota upgraded the cooling system so it runs more efficiently, but it’s the same Nickel Metal-Hydride battery that’s in the second generation Prius.

Emissions: For all you Californians, the 2010 Prius will be certified as a Super Ultra Low Emission Vehicle and an Advanced Technology Partial Zero Emissions Vehicle.

So when my gag order is finally lifted later this month, watch for my 2010 Prius video tour and review of my road test (including hard-to-believe mileage). And for those of you who can’t wait until the end of the month for more Prius coverage, the full specs are listed in the press release [PDF].