1.8 Automatic Hatch here.
I currently have 3,670 miles. I love this car so much. I just get upset with it sometimes when it gives me 26mpg after I get off the freeway after driving about a 25 mile distance going 58mph with no traffic at all no braking. I baby my sonic everyday. That mpg calculator is a liar especially if I reset it. It will say 37mpg but I do the math and its really 24-26mpg.
The highest real calculated mpg I've reached is 33mpg (with ac in low). Then sometimes my fuel gauge likes to play around and a bar comes back after I park then it stays for like five more miles and dissapears for good. In the city I mostly never use ac unless its 90+degrees outside. Sometimes it seems as if this car likes having the ac on. I only pump regular chevron gas. If chevy ever decides to make a diesel sonic, ill be ready to trade in. The sonic would be 110% perfect if the mpg was as the computer says, well on mine :blankface: and if it had cooled seats