Nearly a year ago, we published a gas-mileage review on the Hyundai Ioniq Hybrid, the South Korean brand's Toyota Prius challenger. We saw 49.5 miles per gallon over 565 miles of driving.

Now, we've tested the Ioniq Hybrid in more extreme conditions, on the cold, wintry roads of Detroit, Michigan.

Not only did we cover exactly 400 miles on those frosty roads, we did it during the madness of the Detroit Auto Show, which led us to spend more time than usual driving in stop-and-go city conditions.

DON'T MISS: 2017 Hyundai Ioniq Hybrid: gas mileage review

The Ioniq Hybrid is by far the most common member of Hyundai's three-vehicle Ioniq family, alongside a plug-in hybrid and all-electric model marketed mostly in a handful of states (though available for order nationwide).

The most efficient version of the Hybrid, the base Blue trim, returns 57 mpg city, 59 highway, and 58 combined.

Thankfully, our Detroit test car wasn't the Blue but a range-topping Ioniq Limited. Along with HID headlights, leather upholstery, and a sunroof, it came with heated seats, a must-have during a Detroit January.

2017 Hyundai Ioniq Hybrid

2017 Hyundai Ioniq Hybrid

2017 Hyundai Ioniq Hybrid

2017 Hyundai Ioniq Hybrid

2017 Hyundai Ioniq Hybrid

2017 Hyundai Ioniq Hybrid

2017 Hyundai Ioniq Hybrid

2017 Hyundai Ioniq Hybrid

We ran the heated seats for virtually every mile of our testing, but beyond that, we stuck to Eco mode (aside from a handful of times urban traffic conditions required the Sport setting's performance).

The result, over our 400-mile test, was 41.5 miles per gallon, per the built-in trip computer.

That's not only a big drop in the EPA numbers, but a significant decrease from the results of our test in May of 2017. The culprits aren't hard to pinpoint.

WATCH THIS: 2017 Hyundai Ioniq Hybrid video drive review

For a start, the weather during our test was frigid.

While we got the car on the first of two balmy, 50-degree days, the average high during our final seven days was just 29 degrees, with an average low of 16. Abundant snow also made driving more challenging.

According to the EPA, hybrids are up to 34 percent less efficient in cold weather.

2017 Hyundai Ioniq Hybrid

2017 Hyundai Ioniq Hybrid

While our fuel-economy hit wasn't that dramatic, the estimate roughly squares with the 28-percent dip we saw versus the EPA combined rating.

So the cold-weather effect on the performance of the hybrid's battery certainly makes sense.

Beyond simply the weather, there were also the city driving conditions to consider.

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Detroit isn't Manhattan or Los Angeles, but the level of traffic in the downtown area increases considerably during the week leading up to auto show.

Automaker shuttles and car carriers clog the streets in the heart of the city, not to mention the normal grind of big-city driving.

But the cold weather's impact on our battery pack meant the Ioniq didn't drop into all-electric mode as freely at low speeds. Relying on the engine in these conditions likely contributed to the lower fuel economy.

2017 Hyundai Ioniq Hybrid

2017 Hyundai Ioniq Hybrid

While we ended up far below the EPA-estimated fuel economy, it's worth noting how good the Ioniq felt, both in the city and in general.

The battery performance wasn't great, but the electric motor was strong and the Ioniq's compact footprint made it easy to exploit openings in traffic on streets crowded with larger SUVs and pickup trucks.

The Ioniq Hybrid has its charms, and it's still easy ito log more than 40 miles per gallon. We ended up remembering it as a likable car, with more character than a Toyota Prius and a far less polarizing design.