Re: 2011 Sonata GLS HORRIBLE Gas Mileage Well, given the offer you have, I would take Chris (MaxxMPG) up on his offer to see if it is just your drive and the difference between this larger car and the Civic you used to have. If you guys really determine there is an issue, then my prior suggestion may still stand. Doing it to be a PITA isn't going to make your situation any better. I have driven in downtown NYC for exactly 1 day in my entire life, in a rental car (08 or 09 Galant I believe), and I know my MPG tanked as well. KittyBoodles' idea is also a good one... take a drive in a car you know gets better numbers and see how it fares on your commute. There are many untapped options before you go throwing money into a lawsuit On the other hand, part of me feels like you've already written this car and Hyundai off and are gonna do what you're gonna do anyways, and no answer or advice any of us gives you will make you happy.