A custom made Google Sheet to track everything - maintenance, repairs, insurance, and fuel ups. I'd like to move to an app that supports all of the above, but getting everything into an importable format was messy (tried it with Fuelio), and I gave up after a while. The fact that I'm also writing down parts purchased prior to installation does not make this easier.

My plan is to try and convert it all into plaintext accounting format (probably Beancont with a tailor-made plugin), but so far I've been mostly kicking that ball down the street.