If you're looking to save money on gas without giving up the character and versatility of an SUV, these are your best bets in today's SUV marketplace. But which SUVs have the best mpg? We crunched the numbers and came up with the most fuel-efficient SUVs for 20 in a variety of classes and sizes. Today's SUVs benefit from advances in engineering and technology that have increased fuel efficiency by leaps and bounds.