Wealthy environmentalists and those who worry that another gas price spike will make it difficult to enjoy reclining, massaging rear seats will have one less thing to worry about this summer. Mercedes-Benz has created a hybrid-powered version of it super-luxury S-Class line of cars.

Edmunds Inside Line explains, "Mercedes-Benz is redesigning its S-Class flagship sedan for 2010, and the new lineup includes the 2010 S400 Hybrid, the first series-production Mercedes-Benz passenger car with hybrid drive. Mercedes call the S400 Hybrid the ‘world's most economical luxury car with a gasoline engine,' estimating its combined fuel consumption at 29 mpg."

Mercedes' hybrid claims a few technological innovations not found in other hybrids for sale today. Motor Trend notes, "The new S400 Hybrid receives power from a 3.5L V-6 mated to a seven-speed automatic and an electric motor with a lithium-ion battery." While many other manufacturers are developing lithium-ion cells, none have yet reached production. If Mercedes meets its target date to sell this car this summer, it may be the first car for sale in the U.S. with a functioning li-ion battery. "Output is 295 hp and 284 lb.-ft. of torque, with the electric motor contributing 20 hp and 118 lb.-ft." The S400 Hybrid also features "a start-stop system and regenerative braking," like many other hybrids, but "the hybrid system resides in the engine bay and doesn't compromise trunk or interior space." That gives it an advantage over its only super-luxury rival, the Lexus LS600h, which compromises trunk space to house its batteries.

The rest of the S-Class lineup persists with a mild facelift and some engineering upgrades. Autoblog reports, "The 2010 S-Class line-up will include the 382-hp, V8-powered S550 in both rear- and all-wheel drive spec, along with the 518-hp S63 AMG, the 510-hp S600 and the range-topping, 604-hp S65 AMG." All models "benefit from a subtle exterior makeover," and inside, boast "a myriad of high-tech appointments, including a 6.5-inch color display, a revised COMAND system, navigation, Bluetooth connectivity and a Zagat-rating system for local restaurants." New safety systems are offered as well, including headlights that automatically dim high beams when another car approaches, and an alert system to wake drivers lulled to sleep by those massaging seats.

The 2010 S-Class lineup is scheduled to reach showrooms in August. Prices have not been made public.

If you're in the market for a new car, check out the U.S. News rankings of this year's best cars as well as this month's best car deals.