Range is often discussed when the subject of electric cars comes up, but it's also relevant in the world of internal combustion.

Driving the most economical car in the world would still be a pain if the tank only allowed for fifty miles between trips to the gas station.

If your car could do more than 1,200 miles on a tank though, as Mercedes-Benz has just demonstrated with the E300 Bluetec Hybrid it sells in Europe, you'd probably forget what a gas station looked like.

Journalist Andrew Frankel from Autocar took an example of the car all the way from Tangier in the north of Africa to Goodwood in the U.K. on a single tank of diesel--recording average fuel economy of 61.2 mpg along the way.

That's almost double the 33 mpg combined EPA rating of its non-hybrid equivalent in the U.S, the 2014 Mercedes-Benz E250 Bluetec. It's also higher than the car's official European combined economy of 57 mpg--a rare feat, given the unrealistic testing procedure employed for recording fuel economy in Europe.

MORE: Mercedes-Benz E300 Bluetec Hybrid Sedan: Quick Drive

It's worth noting that the 57 mpg figure isn't entirely down to the hybrid element of the E300 Bluetec Hybrid.

Instead, the challenge played to the strengths of the 2.1-liter diesel engine under the hood--excellent highway cruising characteristics. Frankel's trip involved spending 27 hours behind the wheel. Divide the total mileage of 1,223 by that number and you get an average speed on the journey of 45 mph.

That's likely a factor of the 56 mph cruising speed picked for the challenge, and slow-downs caused by traffic and non-highway sections of the route,

Higher speeds, naturally, would result in lower economy, since it takes much more power to overcome the extra air resistance.

But 1,223 miles is still a huge range on one tank--so how was it possible?

MORE: 2014 Mercedes-Benz E 250 BlueTec Diesel: Fuel-Economy Review

The other factor is the tank itself. In the U.K. and some other countries, buyers can opt for a larger fuel tank to make regular long journeys just that little bit easier. In the case of the car used in the challenge, Mercedes fit an optional (for $170) 21.1 gallon tank.

Other than that though, the car was standard--no extra aerodynamic tweaks, and no taped-up panel gaps. Frankel and the Mercedes had to deal with delays exiting Africa, traffic in France, heavy rain and intense heat.

And E300 Bluetec Drivers don't want for comfort, equipment or performance--with a 201-horsepower diesel engine and 26-horse electric motor, the car's 7.5-second 0-62 mph dash and 150 mph top speed are suitably Mercedes-like.

There are lots of reasons diesel hybrids aren't sold in the U.S, but the E300's abilities are still impressive. And it leaves us wondering what drivers could get from the diesel E250 Bluetec sold in the U.S, on a similar highway cruise...


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