There have been a few fuel economy scandals this year involving automakers—most notably Hyundai and Ford—claiming certain numbers and customers who never saw anything close to those numbers. Because of these, it became clear that the EPA doesn't actually test most of the cars on the market, the agency just trusts that the automakers are telling the truth.
In response to criticism from customers, the EPA has done a massive audit of cars' fuel economy, and plans to release it shortly. Of course, EPA officials are "non-essential" so we'll have to wait until the house representatives manage to complete simple and routine aspects of their jobs.
[via Automotive News]