I guess this site will interest most fuelly users, although im sure there are others that excist too. Its a site that contains all compiled data for emissions and fuel consumption for almost every car available at the moment. It also shows more detailed emissions for every car such as N0X emissions etc, and the MPG figures are also converted for US users too.
If you click on a manufacturer on the left, you can list all the cars they produce in order of fuel consumption, handy if you're looking for a new car, and want to know which car offers the best overall economy. Enjoy!
Just realised when you click a certain manufacturer, it tells you the average fuel consumption and emissions for all models made by that company, example VW: Average fuel consumption 41.9 MPG and average CO2 output 182.2 g/km (based on 4433 models)
The VW with the lowest average fuel consumption is the VW Polo TDI with 83.1 MPG. Pretty cool huh?