We just added the ability to hide cars reporting 0.0 MPG because they don't have fuel-ups yet.
While you're browsing cars, look for the "hide zero mpg" link at the top of the page.
Click it, and you'll get a list of just those cars that are reporting mileage. You can click "show all" to go back to the default listing. We're planning to add this to motorcycle browsing too once there are more motorcycles reporting mileage.
laz, the only problem with having "hide zero" as the default is that some models only have one or two cars with reported mileage. So it's misleading to see Toyota Prius (30) when you're browsing, click it, and only see two or three cars listed. And I don't think we're at the point yet where we can show only those cars listing mileage in the Browse Vehicles listings.