"I want a fuel-efficient car, but I live in a snowy area, and won't buy one without all-wheel drive; what's the best?"

It's a question we hear often.

Whether or not you agree that AWD is a must-have in wintry climes, the selection of cars with high fuel economy and AWD is limited.

DON'T MISS: 2014 BMW 328d xDrive: 40-MPG Diesel Sport Wagon Reviewed

Fuel prices may be cheap at the moment, but six years of steadily rising corporate average fuel economy rules have had an effect on EPA ratings for 2017 vehicles.

For many years, the Subaru Impreza compact sedan and hatchback had the highest EPA ratings for gas mileage among all-wheel-drive vehicles.

But a couple of new entries leapfrog Subaru's most efficient vehicle, which for 2017 remains the Impreza, at 31 mpg combined.

2016 Toyota RAV4 Hybrid, Catskill Mountains, NY, Feb 2016

2016 Toyota RAV4 Hybrid, Catskill Mountains, NY, Feb 2016

The Toyota RAV4 Hybrid, when fitted with AWD, comes in at 32 mpg combined, and has been selling in large numbers since its launch two years ago.

But there's another vehicle that tops even Toyota's hybrid compact crossover—though, admittedly, you'll be hard-pressed to find one much below $50,000.

As this EPA fuel-economy ratings comparison shows, the most fuel-efficient vehicle (without a plug) this year is the 2017 BMW 328d xDrive diesel wagon fitted with all-wheel drive.

READ THIS: 2016 Toyota RAV4 Hybrid: Gas Mileage Review

The 328d xDrive wagon (as well as the sedan model of the same car) comes in at 34 mpg combined.

That's high for an AWD vehicle: 2 mpg combined better than the RAV4 Hybrid and 3 mpg better than the Impreza 5-door.

The Impreza's crossover sibling, the higher and body-cladded 2018 Crosstrek, comes in lower yet, at 29 mpg combined.

2018 Subaru Crosstrek, 2017 Geneva auto show

2018 Subaru Crosstrek, 2017 Geneva auto show

2017 Subaru Impreza, Pacific Southwest Railway Museum, Campo, California, Dec 2016

2017 Subaru Impreza, Pacific Southwest Railway Museum, Campo, California, Dec 2016

2017 Subaru Impreza, La Jolla, California, Dec 2016

2017 Subaru Impreza, La Jolla, California, Dec 2016

Note that the BMW will be considerably more expensive to buy than any of the other three.

Consequently, its total cost per mile will vary a lot depending on your local difference between diesel fuel and gasoline (which varies from state to state), how many miles you drive, and how long you keep your car.

CHECK OUT: 2017 Subaru Impreza: first drive of AWD compact sedan, hatch

Still, in terms of sheer rated fuel economy, the BMW 328d xDrive pair are the AWD fuel-economy champions this year. (Don't call it "gas mileage" ...)

Over to you, Subaru.

[hat tip: Steve Wann]

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