By Jason Siu

GM could have overstated fuel economy figures in more than two million vehicles.

Last week, the company issued a stop-sale order on the Chevrolet Traverse, GMC Acadia andBuick Enclave models, saying that the EPA labels on them were incorrect and had overstated mpg claims. Consumer Reports found it peculiar that the issue only affected the 2016 model year vehicles, considering GM hasn't made any significant updates to any of those three models. Which means the correct 2016 label will have worse fuel economy compared to the 2015 model, despite the 2016 models not being a significant refresh.

It seems unlikely that GM would have changed the powertrain in the affected vehicles from 2015 to 2016, especially in a way that would make their fuel economy go down. The publication has tested all three vehicles and noted that their real-world fuel economy figures are more in line with the new 2016 numbers than what's shown on the labels for previous years.

The big issue is that if the overstated mpg claims impact previous models, that means more than two million vehicles could have incorrect fuel economy figures. A similar issue happened to Hyundai and Kia in 2012, when the EPA spot checked and found overstated fuel economy numbers. The Korean automaker compensated owners with debit cards to pay for the estimated additional fuel costs based on the actual miles driven and added 15 percent on top.

If GM ends up having to do the same, it could prove costly. Overstated fuel economy figures could cost some customers up to $1,000 over years of ownership, since the EPA's calculator on fueleconomy.gov notes that a decline from 19 mpg overall to 17 mpg overall would cost an average consumer $200 a year.

This story originally appeared at AutoGuide.com