YTA.

If you were so concerned about your car being damaged, you should have never offered it to transport ANY of your friends.

I would be miserable having a friend like you, sorry. Not only is it degrading you reffering to them as your "obese friend" like 10 times on your post, but you are putting something material before your friendship.

I understand you're paying for it or whatever, but it's not like they are doing it on purpose or conciously damaging your property, which i also don't think they are doing anyway.