If you're into suv gas mileage comparison charts, you might as well avoid those beautiful H2s if you're in search of the best gas mileage SUV. You might have to take a step down to the H3 for better gas mileage. Generally the larger scale vehicle you go, the more it costs to fill that tank. Not to mention the massive V8s they stick in them. These engines are gas hogs! So when you're out doing a bit of window shopping, remember that bigger is not always better when it comes to SUVs.