2011 Mercedes-Benz S400 Hybrid

Super luxury cars aren’t known for Prius-like fuel efficiency, so when a 2011 Mercedes-Benz S-Class Hybrid showed up at our office, I thought it was the perfect opportunity to see what could be expected from a big hybrid on the open road.

Usually, automakers charge a premium for hybrid versions of their gas models, but with a $91,000 base price, the S400 Hybrid is the least expensive S-Class that Mercedes sells. Our test car gets an EPA-estimated 19/25 mpg city/highway. That’s 26.6 percent better around town than the non-hybrid S550’s 15/23 mpg city/highway ratings.

Morty was jealous of the optional multicontour front seats, which offer heat, ventilation and massage.

My girlfriend, brother, dog and I all buckled up to test out the S-Class Hybrid’s highway numbers on a road trip from Arlington, Va. to my mom’s hometown of Chicora, Pa. The trip works out to 274 miles each way, and the S400 averaged 26.2 mpg through the Allegheny Mountains and back.

While the S400 beat its fuel economy estimate on the highway, some of its competitors could probably do better. The base Porsche Panamera, Audi A8 and S400 all share the same annual fuel cost of $2,927. Although the city numbers for the Audi and Porsche can’t match the Mercedes, they get two mpg more on the highway.

This Mercedes tops the super luxury car class in fuel economy, but I wouldn’t call it green. The EPA estimates the S400 emits 8.9 tons of carbon dioxide annually. That’s the same amount as a Ford Mustang GT and considerably more than the Prius’ 3.8 tons. Cars like the Infiniti M Hybrid split the difference at 6.5 tons. If you’re shopping for a high-end luxury sedan, the S400 will likely impress, but if your goal is an eco-friendly car, you might spend less green to stay green.