TRAVERSE CITY, MI – General Motors claims its new Chevrolet Cruze Turbo Diesel sedan achieves 46 mpg (5.1 L/100 km), the best highway mileage of any non-hybrid in the U.S.

That makes it the perfect vehicle for our annual Detroit-to-Traverse City test drive: A 250-mile (402-km) jaunt to Northern Michigan that includes almost zero city driving.

WardsAuto reviewed the Cruze Turbo Diesel in July during the car’s U.S. press launch, but we wanted to put its long-haul numbers to the test, especially because auto makers’ mileage claims have come under fire of late for not living up to the real-world experience of vehicle owners.

GM also brags the Cruze’s diesel fuel economy beats its chief competitor, the Volkswagen Jetta TDI diesel, rated at 42 mpg (5.6 L/100 km) on the highway.

During a shorter and more varied test drive, 42 mpg was the best overall mileage WardsAuto editor James Amend was able to attain with the Cruze Turbo Diesel, which made us want to do more testing. Plus, the pre-production vehicle he drove conked out due to an early assembly-line glitch that was corrected before production of salable vehicles began.

So we put on our professional skeptic’s hat, topped off the tank on our $25,795 test car (including $810 destination charge) and pointed the nose north. We also vowed not to operate the car any differently than a typical driver with moderate concerns about efficiency.

That means we rarely drove faster than 75 mph (121 km/h), but we also did not resort to any hyper-miling tricks or clog up traffic by driving 55 mph (89 km/h). We did test the acceleration and high-speed-passing power on a number of occasions, which dinged our mileage average a bit.

After some drivers gave us the stink-eye for briefly slowing to 65 mph (105 km/h) in one of the middle lanes of the expressway, we decided 70 mph (113 km/h), the speed limit for most of the roads on our journey, was a fair average pace for evaluation.

The result: The Cruze Turbo Diesel exceeds the highway mileage number on its sticker. We lose about 1 mpg (0.4 km/L) from our average, as well as average velocity because the last leg of our trip is quite hilly and not conducive to fuel economy.

But as our drive ends at the site of the CAR Management Briefing Seminars here, the trip computer registers 46.7 mpg (5.0 L/100 km) after 253 miles (407 km), with an average speed of 64.9 mph (104 km/h).

Even better, we only burned a quarter-tank of fuel. When the needle on the fuel indicator did not move from “full” after 100 miles (161 km) we were impressed, but when the needle still had not budged after 150 miles (241 km), we honestly thought the gauge was broken (apologies to GM engineers).

We’ve driven a lot of vehicles to Traverse City in August for the past 30 years, and the Cruze Turbo Diesel is the first one to arrive with the fuel tank still three-quarters full.

Our journey leaves us feeling more positive overall about the future of diesel-powered passenger cars in the U.S. Thanks to advances in emissions technology, diesels can be as clean, or cleaner, than comparable gasoline engines, and they now are mainstream enough to appeal to American consumers.

Editor Steve Finlay was impressed as well with the diesel-powered Volkswagen Touareg midsize SUV he drove here from Detroit.

Finlay reports mileage as high as 29.2 mpg (8 L/100 km) before logging an average 27.4 mpg (8.6 L/100 km). Not bad for a hefty utility vehicle with 406 lb.-ft. (550 Nm) of torque and a tall profile that hinders aerodynamics.

The Touareg’s exhaust, like the VW Passat diesel, is very clean, Finlay points out. It uses a selective catalytic reduction system that reduces oxides of nitrogen and other emissions by as much as 95%.

Critics point to the relatively steep price of the Cruze diesel, about $2,600 more than a base VW Jetta diesel equipped with a 6-speed manual transmission.

But a big chunk of the premium comes from Chevy’s use of a SCR emissions-control system. The Jetta currently does not use a SCR system, but it will need one soon to meet upcoming European and California regulations.

Other premium features on the Cruze include a 6-speed automatic transmission, upscale leather upholstery and fabulous front seats. Extra-firm and supportive without any gimmicks, they are perfect for long-distance drivers and helped make our trip this year an easy one.

But clearly, the Cruze Turbo Diesel is not for everyone. At idle and in slow-moving traffic, there is no hiding the fact the car is in fact a diesel. It vibrates more at idle than a comparable 4-cyl. gasoline engine, and mild vibration can be felt in both the steering wheel and through the seats, especially when the engine is cold.

At any temperature, it grunts like a diesel when it launches and when traveling at low speeds. For car buyers who do not like this reality, the test drive likely will end before the car leaves the dealership parking lot.

But such minor unpleasantries are more than compensated for by the 2.0L diesel’s boatload of torque and near silent operation while cruising at highway speeds. And of course, there is the fuel efficiency and nearly unbelievable range: 700 miles (1,127 km) or more on one tank.

GM officials admit the Cruze Turbo Diesel is a cautious “toe in the water” in the U.S., and they are uncertain what the next move will be. After our successful drive, we can advise the auto maker to dip more than a toe. The water looks fine.

dwinter@wardsauto.com