Fuel economy is one of the largest deciding factors for many consumers, especially as gas prices continue their relentless march upward. And over the past few years, 40 mpg highway has become the new "it" number for automakers to brag about in their marketing campaigns. Kia and Hyundai have been no exception, with the latter loudly trumpeting its claims. The Hyundai Elantra has been at the forefront of the brand's 40 mpg advertisements, and will likely be a central focus of the controversy. It's important to note that for most of our tests, our editors put their foot into the throttle hard to evaluate acceleration, engine noise, etc. But a year-long evaluation, especially for a compact commuter car like the Elantra, is a different story. As was our recent 40 MPG test, which is one of several recent tests featuring Hyundai and Kia vehicles that we've outlined below.

2012 Hyundai ElantraLimited - Old EPA Rating: 29/40/33 mpg (city/highway/combined), New EPA Rating: 28/38/32 mpg, MT Fuel Economy: 26.5 mpg

Our long term Hyundai Elantra is a car I'm intimately familiar with. I took it on multiple trips up and down the West Coast. My first trip, to Portland, Oregon, and back netted 28.6 mpg in about 2000 miles of mostly highway driving - far shy of the old 40 mpg rating. So I decided to try again, this time with a hypermiling run down the mostly flat and straight section of I-5 from Redding, Calif. to Los Angeles. After seven agonizing hours of driving with the windows up, A/C off, and cruise control set to 70 mph (the speed limit), I managed to achieve 39.77 mpg - by far the best fuel economy we observed with our recently departed Elantra. In fact, over its one year and over 23,000 miles with us we averaged just 26.5 mpg - still well shy of the new 32 mpg combined rating.

2012 Hyundai ElantraGLS - MT Fuel Economy: 35.4 mpg

With outcry from groups like Consumer Watchdog and armed with the real-world numbers from our Elantra, we decided to put the compact up against the Chevrolet Cruze Eco, Ford Focus SFE, Honda Civic HF, Mazda3 Skyactiv, and Volkswagen Jetta TDI in our 40 MPG Madness comparison test, where it finished dead last with the lowest observed fuel economy of 35.4 mpg, despite days of scientific hypermiling. This test was specifically designed to measure how close each vehicle could get to the 40 mpg number, no lead foots were allowed.

We're not the only ones that have noticed significantly lower-than-advertised fuel economy figures in the Elantra; a quick look at Fuelly.com reveals that the average self-reported mpg for the 2011-2013 Elantra is hovering right around 30 mpg. The self-reported mileage on the EPA's FuelEconomy.gov mirrors Fuelly's findings.

2011 Hyundai SonataHybrid - Old EPA Rating: 35/40/37 mpg, New EPA Rating: 34/39/36 mpg, MT Fuel Economy: 27.0 mpg

Back when the Toyota Camry and Volkswagen Passat debuted, we decided to compare the fuel-sipping versions (the Hybrid and TDI, respectively) with the Sonata Hybrid, the then-new kid on the block. In our testing, the Sonata Hybrid had the worst observed fuel economy by far - a miserable 27.0 mpg.

2012 Hyundai AccentSE - Old EPA Rating: 30/40/34 mpg, New EPA Rating: 28/37/32 mpg, MT Fuel Economy: 32.4 mpg.

MPGate hasn't just affected the Elantra and Sonata Hybrid, the sub-compact Accent has also come under fire. Though our manual-equipped tester finished first in our subcompact sedan comparison test, our 32.4 mpg observed fuel economy was below the old 34 mpg combined average; the new 32 mpg matches the fuel economy we saw.

2012 Hyundai Veloster- Old EPA Rating: 28/40/32 mpg, New EPA Rating: 27/37/31 mpg, MT Fuel Economy: 27.6 mpg

The Veloster is yet another model that loses its 40 mpg rating in MPGate, being downgraded to just 37 mpg. In our real-world testing during our oddball comparison test, the Veloster achieved 27.6 mpg, still a bit below the new 31 mpg combined figure.

2013 Hyundai VelosterTurbo: Old EPA Rating: 26/38/30 mpg, New EPA Rating: 24/35/28 mpg, MT Fuel Economy: 25.2 mpg

In our comparison test with the Mini Clubman S, the Veloster Turbo achieved just 25.2 mpg - about 5 mpg worse than the Mini, despite at the time having better fuel economy numbers.

2012 Kia Rio: Old EPA Rating: 30/40/34 mpg, New EPA Rating: 29/37/32 mpg, MT Fuel Economy: 30.8 mpg

The popular Kia Rio has also been affected by the fuel economy revisions. In the same comparison test where its Hyundai Accent kissing-cousin won, the Rio came in dead last. Though the EPA's revision was kinder to the Rio than it was the Accent, we still achieved worse fuel economy in the Rio than we did in the Accent at 30.8 mpg observed.

2012 Kia SportageEX: Old EPA Rating: 22/32/25 mpg, New EPA Rating: 21/30/25 mpg, MT Fuel Economy: 15.8 mpg

Car models from Hyundai and Kia may have been hit hard by the EPA revisions, but their CUVs have also suffered. The most recent Korean crossover we tested was the front-drive Sportage EX in our Compact Crossover Comparison test, where it placed fifth. While the new EPA numbers for the Sportage might be more realistic, we averaged just 15.8 mpg in our tester, by far the worst observed fuel economy in the test.

So where does MPGate go from here? That remains to be seen. While Hyundai and Kia are owning up to the mistakes and financially compensating customers of affected vehicles, it's safe to say that their rapidly rising reputations and soaring sales are likely to take a hit. Check out our rundown of observed fuel economy in the chart below.

Model	Test	Old EPA MPG	New EPA MPG	Observed MPG
2011 Hyundai Elantra Limited (automatic)	Best-Selling Compact Sedan Comparison	29/40/33 mpg	28/38/32 mpg	25.7 mpg
2011 Hyundai Sonata Hybrid	Midsize Sedan MPG Comparison	35/40/37 mpg	34/39/36 mpg	27.0 mpg
2012 Hyundai Accent SE (manual)	Economy Five-Door Hatchback Comparison	30/40/34 mpg	28/37/32 mpg	32.4 mpg
2012 Hyundai Elantra Limited (automatic)	Long Term Test	29/40/33 mpg	28/38/32 mpg	26.5 mpg
2012 Hyundai Elantra GLS (automatic)	40 MPG Compact Sedan Comparison	29/40/33 mpg	28/38/32 mpg	35.4 mpg
2012 Hyundai Veloster (manual)	Oddball Comparison	28/40/32 mpg	27/37/31 mpg	27.6 mpg
2013 Hyundai Veloster Turbo (manual)	Misfit Comparison	26/38/30 mpg	24/35/28 mpg	25.2 mpg
2012 Kia Rio (manual)	Economy Five-Door Hatchback Comparison	30/40/34 mpg	29/37/32 mpg	30.8 mpg
2012 Kia Sportage EX (FWD, naturally aspirated, automatic)	Compact Crossover Comparison	22/32/35 mpg	21/30/25 mpg	15.8 mpg

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