BMW is the latest automaker that was discovered by the Environmental Protection Agency (EPA) to have inaccurate fuel economy labels on the windows of its vehicles.

The EPA has ordered BMW to alter the fuel economy ratings of four of the company’s 2014 Mini Cooper cars.

The agency conducted an audit on the ratings of the new Mini Coopers and ran its own tests at the National Vehicle and Fuel Emissions Laboratory in Michigan. The values derived were said to be different from the ones submitted by BMW for certification and indicated in window stickers of the vehicles.

The affected vehicles include the 2014 Mini Cooper hardtop and Mini Cooper S hardtop models. These models have three doors and are built with a manual and automatic transmission.

As a result, BMW will now have to conduct new tests on emissions and fuel economy values for the Coopers.

The EPA has instructed BMW to indicate the new and lower ratings on the window stickers of their vehicles. A spokesman for the automaker said that new labels for the company's in-stock 2014 models have already been sent to dealers.

The discrepancy varies from one to four miles per gallon (MPG), the value of which depends on the model and whether it had automatic or manual transmission.

The latest ratings reveal that the Mini Cooper with automatic transmission has a combined driving rate of 32 MPG, with city driving at 28 MPG and highway driving at 39 MPG.

For the automatic Mini Cooper S, the new rating for combined driving is 30 MPG, with city driving at 26 MPG and highway driving at 35 MPG.

According to BMW, the company's mileage estimates were higher than the results achieved by the EPA because the automaker's data on engine-transmission friction, tire rolling resistance and wind drag have lower figures compared to the ones that were calculated by the agency.

It's not clear whether the error was intentional or an honest mistake. It is up to the EPA's Office of Enforcement to decide if a further investigation is essential.

"Fuel economy values matter to consumers and automakers," says Christopher Grundler, director of the EPA's office of transportation and air quality.

"To provide consumers with the most accurate, reliable and repeatable fuel economy values, we are continuing to strengthen our oversight to ensure fair competition among automakers."

Other companies that have been ordered by the EPA to lower their vehicles' fuel economy ratings due to discrepancies include Ford, Kia, Hyundai and Mercedes-Benz.