Need another data field. How about a field in the database to keep track of odometer readings? We could correlate the 'dropping off' of mileage with age and mileage. I have a '99 Mystique and if I play right, can still get 30 mpg. Others show mid twenties, and I have 220,000 miles on mine. I'd like to see other's odo, too.
We have two methods of tracking mileage at Fuelly: tripometer and odometer. So many people are already adding odometer readings every time they add a fuel-up. I'm not sure what a 2nd odometer field would provide.
You could always switch to tracking with odometer readings, and then others would be able to see where you're at. But I think people who choose to track with tripometer readings don't have much incentive to add more data to the system.
I think boethos wants some way to correlate his efficiency with his car's mileage. I could imagine another label along the bottom of the Recent Fuelups graph that displays the car's mileage for each fuelup.
People who currently don't track with the odometer would need to set some start date to their mileage, such as "Today my odometer said X", and then the system would fill in their mileage for past fuelups. Then they could keep using the tripometer method.
The problem is that with tripometer tracking there's no way to know if the fuel-ups are all in a row or not. So someone could say that their odometer says x on a certain date, but that doesn't necessarily mean that they track every single fuel-up from that point on.
The nice thing with tripometer tracking is that you don't need as much discipline. If you miss tracking a fuel-up here or there it isn't going to cause any problems. But with odometer tracking you have to report every fuel-up, or mark "missed a fuel-up" if you miss some, or you'll have wildly inaccurate data.
I don't think we need to add that kind of pressure/data-checking to the tripometer trackers when they already have the option to switch over to odometer tracking if they need to be more precise.