8. Mercedes-Benz GL450: $110.09
The big V8 in the Mercedes-Benz GL450 isn’t the most frugal around with a rating of 15 mpg combined. If you’re considering one of these big Benz’s you’ll be filling it up quite often. With a tank the same size as the Cayenne at number 9, and its desire for the good stuff (premium) you’re looking at the same price to fill up: $110.09. However it gets considerable lower driving range than the Cayenne with 581 miles of road to one tank.