The Cider Squeezy and the parade floats count as cars... at least in my headcanon. I figure if Rainbow Dash can mention guns without us ever seeing any, cars can too. That's if you don't count the aforementioned vehicles.
You forgot about the taxi's in both Putting Your Hoof Down and Rarity Takes Manehattan also yay new series.
dont forget in Hearts and Hooves day when Big Mac and Cheerilee are at the bottom of the hole we can see a buried rubber tyre... When carts and stuff have wooden wheels... Hmm... EDIT : added a picture
First you wriggle tail oink oink oink then you wriggle your snout oink oink oink then you wriggle your rump oink oink oink then shout it out oink oink oink...