Newbie Fuel economy and Trip computer

[OldSubi]

Hi there!
I have an old Subaru that I have been restoring/upgrading for camping and general escaping to nature in, I found myself here trying to revamp the “trip computer” that was more of a marketing gimick (1984) than a functioning addition to a car made for 4WD'ing where a real trip computer would be very handy.
MPGuino seems like a good basic project to start learning Arduino c,

Cheers