I have one active vehicle and several in my garage. On the settings page I do not have an option to change my primary vehicle. I added a fuelup via SMS, and it was assigned to one of the cars in my garage.
What about using SMS for two active vehicles? Is that a possible extension on what is done now? Maybe a simple numbering system for the vehicles, then the MPG info. Something like "1 83000 3.119 11.298 ", where the first number entered is the vehicle number on the user account. Would make it easier than entering the vehicle into the notes, then moving it if it's not the primary vehicle on the account.
phydeaux, that's something we'd like to do eventually. But right now we're keeping the system as simple as possible. We don't want to add another option, because that's one more thing you can potentially get wrong in an already fairly complex system.
We're going to keep what we have running for a while and make sure things are solid before we move to another version. But multiple vehicles via SMS is on our long-range to-do list.