heh, we work on the site when we can. But 99% of our development time goes into our sister site Metafilter.com. That sites pays the bills and makes Fuelly possible. We're only a couple of people and Fuelly is a side project so we do what we can here.
The problem with adding info is that vehicle profile pages are pretty tight. So we can't just add totals for all the years, where would they go? A new row of boxes for year totals? What about folks who have just two years? Or three? Or eight? Would empty boxes look good? Maybe, maybe not. So any addition to the site requires some time to think through questions like this and find the best way to add that information to the site and have it work with the existing design. It's not impossible, just something that requires time.
That's simple really. Just make a "Total Garage Stat's" page. It can be linked in the profile and over on the left menu under "Your Garage", or even under "Your Info".
Within, you can have total costs both as a grand total and a yearly, total mileage driven, average MPG/ 100l/K, etc. Both as a grand total and/or yearly totals, if people used tags, you can list them by most popular, etc. I use the tags to identify the gas station I buy the gas from for example.
Time I understand, having managed a few sites already. It can be absolutely crazy to keep up! And certainly you have to have a bread winner to keep sites such as these going! lol
But, if you guys ever need assistance, by all means ask.
I think it'd be cool for someone to take our Fuelly export format as an import and generate some reports like the ones you describe. We have our own reporting plans in the works, but in the meantime if anyone out there wants to code something up I think a few Fuelly folks would give it a shot. Not everything has to happen on our site, and I think there's plenty of room for folks outside of Fuelly to take what we have as a starting point and run with it.