Yeah, we had a very basic car sharing bit of code in place and ready to go, but it opened up a bunch of potential problems down the road (what to do if you sell the car/break off the relationship, etc) that we didn't release it on day one.
I'm wanting the feature as well, since I'm currently tracking my wife's car and she has to tell me her details to enter, so I suspect we'll hammer out the problems we couldn't solve before launch and add it in the next week or so.
I really like the site so far! A lot more features than Fuelfrog! Though it would be nice to have Twitter integration - the mobile entry is a little cumbersome. Using Fuelfrog, I loved being able to tweet my fill ups. Thanks for a great concept.
I think you guys should track where the gas was purchased and at what price. So that if someone finds a cheap gas station in our area we'd get notified. Like grab a zip code or city name where we live, and enter the zip of the gas station if known, then tell people, hey someone just got gas for $3.89 near you at a BP station on Blue Heron Blvd in Riviera Beach, FL, that's 10 cents less per galon then your last fill up. It'd be too cool if you could somehow incorporate Google Maps Mobile Current Location feature to help us enter the location details too.
What I would like is a meter for my car (on a mobile phone or gps) that shows me how much I've spent on gas so far this trip. Doesn't have to be too accurate, I just want to see I spent $8 running around doing errands this morning.
Is there a correct way to compensate for a missing tank other than to throw out the data? You could try to guess the total gallons used, but that would still be fairly suspect. Unless there is a reasonable way to correct for this, I think the best way to handle it is to encourage users not to enter data when part of it is missing or incorrect and add the ability to flag obviously incorrect data (i.e. missing tanks leading to 70+ mpg on a 25 mpg car).