Like Google Trends? Fuelly Trends would be just as cool.
I'd like to see trends in spending & mileage. If you've ever used Google Reader or Google Trends, it's totally fascinating to see when people check things or when and why things become a popular search. Below is an example of trends, of course Fuelly trends would track gas trends and not internet usage.
It would also be interesting to see how seasons (heating and AC usage) affect mileage or how a certain period in time has lower mileage than others and the user can then determine what made it that way.
That's a very interesting idea, and there might be some ways to show the big picture. Unfortunately, it's not a matter of simply exposing the data we have. For example, gas prices vary widely across different parts of the world, and we don't convert currencies here. So it's difficult to compare spending between, say, the US and UK. But it's something we could work toward, and we could limit our sample to one country at a time. Also, fuel economy varies significantly between models so I'm not sure that knowing our collective average MPG tells us much.
We have an admin interface that tells us some global statistics about signups, fuel-ups, and vehicle creation across the system. Maybe exposing some more numbers about fuel-up frequency and how people are using the site would be a step toward spotting trends. I agree that there must be some ways we can analyze what people are adding to visualize a bigger picture.