Gas mileage is a lower priority than luxury in the Hyundai Equus, which comes in a sole drivetrain configuration--unlike the cars it names as competition.
The 2014 Equus posts EPA-certified fuel economy of 15 miles per gallon city, 23 miles per gallon highway, or 18 mpg combined. Its sole source of power is a 5.0-liter V-8, and since it's coupled to an eight-speed automatic, the numbers are about as good as they can get.
In real-world use, we've seen as much as 18 mpg in a mix of canyon runs and interstate strafes.
Hyundai has other hybrid vehicles, but no such model is planned for the Equus lineup.