I can definitely see how this would be useful. The problem is that it complicates the fuel-up form and I'm not sure we'd have enough people using it to justify that.
With the current system you could store business miles in the notes field. Then, when it's time to add everything up,
export your fuel-ups. Add the notes column up in a spreadsheet program like Excel and you'd have your business miles total. Not as handy as having Fuelly calculate it for you, but it could work.
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