Pocket Garage HD is one of those apps that's best suited for the iPhone, but the HD version looks pretty sweet on an iPad. This is the first auto maintenance app I've taken a look at in quite a while since Gas Buddy is a mainstay on my iPhone, but Pocket Garage on the iPad is pretty nice and has many of the same features that Gas Cubby does, but with a nicer interface.
The UI features a large odometer with three buttons beneath. This lets you record odometer readings, servicing, fuel and repair. The settings toggle between miles and kilometers, as well as gallons and liters, and record a wide range of currencies, making this useful if you're out of the U.S.
You can keep track of fuel economy, service reminders, repair logs, view an array of charts, fill in basic vehicle information and more. You also can put in your vehicle identification number, license plate number, etc., but no pass code so be cautious when putting in this information.
I tried the free version of Pocket Garage HD and was pleased with it. If you're keeping track of just one vehicle, this is the way to go. There is a US$4.99 pro version that allows tracking of more than one vehicle, but other differences between the free and paid versions aren't made clear through iTunes or through the developer's site, which returns a 404 error.
There also does not seem to be a way to sync between the iPhone and iPad versions, which lessens the usability somewhat. You'll have to export from one app to the other constantly to keep them both in sync. If you want to keep an auto record at home, Pocket Garage HD is good for the iPad. If you've got an iPhone and want to update as you go, you'll need to grab the separate Pocket Garage for the iPhone. Going pro on the iPhone would be another $1.99.