The Equus is neither efficient nor a gas-guzzler when judged against other large, rear-drive sedans. Gas mileage is a lower priority than luxury in the Hyundai Equus, but given its relative discount status, it may still factor into the decision.
The 2015 Equus receives EPA-estimated fuel economy of 15 miles per gallon city and 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. Hyundai does build hybrid vehicles, but no such model is planned for the Equus lineup.
In real-world use, we've seen as much as 18 mpg in a mix of canyon runs and interstate strafes.