Welcome to CleanMPG! The mileage in my Sonata kept increasing incrementally until it hit around 5000 miles. 18-19mpg is not bad if your commute has a lot of traffic lights. My daily driver is the 2011 Elantra and I have demonstrated that when driven "easy", it returns about 20mpg city. Techniques you will learn here increase that to 28-30mpg city. My Sonata is a stick so it can't be directly compared to your SE, but the Elantra provides a good parallel comparison. To hit EPA city, it is important to minimize braking, keep it rolling, learn how to make use of the fuel cut capability, and accelerate gently enough to allow upshifts at 2000rpm. Pump up the tires will help, but is not a requirement. Add a post in the Start Your Journey Here forum, describe your commute a little, and provide your general location. We're happy to help and share the tips and techniques that will help you increase fuel economy.