I just joined and added all of my vehicle records. (I've saved mileage in all my gas receipts for the last 5 years, so this includes my current 2 vehicles, previous 3, and a bunch of rentals.) Great site; definitely makes it easy to visualize the data!
One question occurred to me as I was going through all this... Is there a limit to how many vehicles you can add (either in your garage or retired)? I found a post about that from several years ago but nothing recent.