We have verified that the data are posted correctly as certified by the EPA where the AWD model has a 1 mpg higher highway rating than the FWD version. It isn’t terribly unusual to find data that are not what you would expect. It usually comes down to decisions made when the manufacturer is certifying their vehicle. It can be related to the test vehicles selected which may differ in test weight due to trim level selections, tire options, engine tuning, gear ratios, or whether or not the manufacturer chose to include drive selections like Eco mode to be averaged in.
The EPA and manufactures negotiate some of the details in how vehicles are tested but that information is not included in the data that is sent to us. Also, manufacturers have the option to voluntarily lower any of their estimates and they are not required to provide and explanation. This is not an uncommon practice and can lead to unexpected results. The only ones who could definitively explain why the AWD version has a higher highway rating than the FWD version would be Hyundai because they performed the tests and entered the data into the EPA’s database.
The EPA’s Office of Transportation and Air Quality is responsible for overseeing all vehicle testing and certification:
Vehicle and Fuel Emissions Testing | US EPA