[Infernal]

So I have also meticulously kept track of my mileage, from January 2013 to November 2017 (my wife began driving it in November, and I didn't have an iPhone app to track it prior to 2013). The current average over that time frame is 36.8MPG. Worst tanks I have are when I was only on the interstate, would get 34MPG.

Mine is an '08 - they seem to have gotten heavier in later years. It also has a manual transmission, which offers more flexibility for conserving brakes and fuel. My wife gets more in the 32-34mpg range, but doesn't keep close tabs on it - she also now has a couple car seats and toddlers in the car, so weight penalty.

EDIT: There might genuinely be an issue with your car - I have a 10.8 gal tank as well but routinely get over 400 miles per tank - 370 if I've been driving more aggressively.